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Full text of "Common objects of the microscope"

COMMON OBJECTS OF THE 

MICROSCOP 

hythk Rev; if v J-G.WOOD.^ 




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ILLUSTRATED BY 

TUFFEN WEST, 




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REVISED AND RE-WRITTEN BY E. C. BOUSFIELD 
GEORGE ROUTLEDGE & SONS, Ltd. 



Robert W. Woodruff 
Library 

Special Collections 




EMORY UNIVERSITY 



COMMON" OBJECTS OF 
THE MICROSCOPE 





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VIII. 



COMMON OBJECTS OF 
THE MICROSCOPE 



BY THE LATE 

Eev. J. G. WOOD, M.A., F.L.S., Etc. 

AUTHOR OF 

'COMMON OBJECTS lit' THE COUNTRY" "COMMON OBJECTS OF THE SEA-SHORE " 

"MY" FEATHERED FRIENDS " ETC. ETC. 



WITH ILLUSTRATIONS BY TUEFEN WEST 



REVISED AND RE-WRITTEN BY 

E. C. BOUSFIELD, L.R.C.P. (Lond.) 

AUTHOR OF 
'a GUIDE TO THE SCIENCE OF PHOTO-MICROGRAPHY" 



WITH ADDITIONAL ILLUSTRATIONS BY THE EEVISER 



LONDON 

GEORGE ROUTLEDGE & SONS, Limited 
Broadway House, Carter Lane, E.C. 



PREFACE TO THE SECOND EDITION 



The task of revising and bringing up to date a work 
which has been the guide, philosopher, and friend 
of thousands of commencing microscopists has been, 
in the present case, one of no small difficulty. 
On the one hand, there was the natural desire to 
interfere as little as possible with the original work ; 
and on the other, the necessity of rendering avail- 
able, to some extent at least, the enormous advance 
in every department which has taken place in the 
thirty-six years which have elapsed since the work 
was first offered to the public. The reviser has 
done his best not only to fulfil these two objects, 
but to keep in view the original purpose of the 
book. 

In the popular department of pond-life especially, 
about fifty new illustrations have been added, mostly 
from the reviser's own notebook sketches. The 
whole of the botanical part has been revised by one 



VI PREFACE TO THE SECOND EDITION 

of our first English authorities, and, in short, nc 
effort has been spared to make the work as accurate 
as its necessarily condensed form permits of. It is 
hoped, therefore, that it may be found not less 
useful than its predecessor by those for whom it is 
alone intended, 



PREFACE TO THE FIRST EDITION 



In my two previous handbooks, the " Common 
Objects " of the Sea-shore and Country, I could 
but slightly glance at the minute beings which 
swarm in every locality, or at the wonderful 
structures which are discovered by the Microscope 
within or upon the creatures therein described. 
Since that time a general demand has arisen for 
an elementary handbook upon the Microscope and 
its practical appliance to the study of nature, and 
in order to supply that want this little volume has 
been produced. 

I must warn the reader that he is not to expect 
a work that will figure and describe every object 
which may be found on the sea-shore or in the 
fields, but merely one by which he will be enabled 
to guide himself in microscopical research, and 
avoid the loss of time and patience which is almost 
invariably the lot of the novice in these interesting 
studies. Upwards of four hundred objects have 
been figured, including many representatives of 
the animal, vegetable, and, mineral kingdoms, and 



Via PREFACE TO THE FIRST EDITION 

among them the reader will find types sufficient for 
his early guidance. 

Neither must he expect that any drawings can 
fully render the lovely structures which are revealed 
by the microscope. Their form can be given faith- 
fully enough, and their colour can be indicated; 
but no pen, pencil, or brush, however skilfully 
wielded, can reproduce the soft, glowing radiance, 
the delicate pearly translucency, or the flashing 
effulgence of living and ever-changing light with 
which God wills to imbue even the smallest of His 
creatures, whose very existence has been hidden for 
countless ages from the inquisitive research of man, 
and whose wondrous beauty astonishes and delights 
the eye, and fills the heart with awe and adoration. 

Owing to the many claims on my time, I left the 
selection of the objects to Mr. Tuffen West, who 
employed the greater part of a year in collecting 
specimens for the express purpose, and whose well- 
known fidelity and wide experience are the best 
guarantees that can be offered to the public. To 
him I also owe many thanks for his kind revision 
of the proof-sheets. My thanks are also due to 
Messrs. G. and H. Brady, who lent many beautiful 
objects, and to Messrs. Baker, the well-known 
opticians of Holborn, who liberally placed their 
whole stock of slides and instruments at my dis- 
posal. 



CONTENTS 



CHAPTER I 

PAUR 

Pleasures and Uses of Microscopy — Development of the 

Microscope — Extemporised Apparatus .... 1 

CHAPTER II 

Elementary Principles of Optics — Simple Microscopes — Com- 
pound Microscope — Accessory Apparatus — Cover-glasses 
— Troughs — Condensers — Dissection — Dipping - tubes — 
Drawing — Measurement ....*. 7 

CHAPTER III 

Examination of Objects — Principles of Illumination — Mirror 
and its Action — Substage Condenser — Use of Bull's-eye 
— Opaque Objects — Photography of Microscopic Objects 28 

CHAPTER IV 

Vegetable Cells and their Structure — Stellate Tissues — 
Secondary Deposit — Ducts and Vessels — Wood-Cells— 
Stomata, or Mouths of Plants — The Camera Lucida, and 
Mode of Using — Spiral and Ringed Vessels — Hairs of 
Plants — Resins, Scents, and Oils — Bark Cells . . 37 

CHAPTER V 

Starch, its Growth and Properties — Surface Cells of Petals — 

Pollen and its Functions — Seeds 63 

ix 



X CONTENTS 

CHAPTER VI 

FAQB 

Algse and their Growth — Desmidiaceae, where found — 
Diatoms, their Flinty Deposit — Volvox — Mould, Blight, 
and Mildew — Mosses and Ferns — Mare's-Tail and the 
Spores — Common Sea-weeds and their Growth . . 78 

CHAPTER VII 

Antenna!, their Structure and Use — Eyes, Compound and 
Simple — Breathing Organs — Jaws and their Appendages 
— Legs, Feet, and Suckers — Digestive Organs — "Wings, 
Scales, and Hairs — Eggs of Insects — Hair, Wool, Linen, 
Silk, and Cotton — Scales of Fish — Feathers — Skin and 
its Structure — Epithelium — Nails, Bone, and Teeth — 
Blood Corpuscles and Circulation — Elastic Tissues — 
Muscle and Nerve 96 

CHAPTER VIII 

Pond-Life — Apparatus and Instructions for Collecting Objects 

— Methods of Examination — Sponge — Infusoria 132 

CHAPTER IX 

Fresh-water Worms — Planarians — Hydra — Polyzoa — Rotifers 

Chajtonotus — Water-Bears 114 

CHAPTER X 

Marine Life — Sponges — Infusoria — Foraminifera — Radiolaria 
— Hydroid Zoophytes — Polyzoa — Worms — Lingual Rib- 
bons and Gills of Mollusca — Star-Fishes and Sea-Urchins 
— Cuttle-Fish— Corallines — Miscellaneous Objects . 154 

CHAPTER XI 

Hints on the Preparation of Objects — Preservative Fluids — 

Mounting Media — Treatment of Special Objects . . 168 

CHAPTER XII 
Section-Cutting— Staining 179 



INDEX OF PLATES 



rbATB 

I. 

II. 

III. 

IV. 

v. 

VI. 

VII. 
VIII. 

IX. 
X. 
XI. 
XII. 
XIII. 
XIV. 



FRESH-WATER AND MARINE LIFE . 
BLOOD, BONE, CARTILAGE 
POLAR. ISED OBJECTS 
FORAMIN'IFERA, ETC., ON DARK GROUND 

INFUSORIA . 

ROTIFERS, WORMS, ETC, , 





r.MiR 


Facing page 2 


n 


52 


ii 


64 


it 


80 


ii 


94 


it 


104 


») 


112 


Front, 


ispkce 


Facing page 132 


»i 


123 


»> 


163 


, 


156 


i) 


140 


ii 


152 



COMMON OBJECTS OF THE 
MICROSCOPE 



CHAPTER I 

Pleasures and Uses of Microscopy — Development of the 
Microscope — Extemporised Apparatus. 

Within the last half-century the use of the 
microscope, not only as an instrument of scientific 
research, a tool in the hands of the investigator 
of the finer organisation of the world of nature, 
nor even as an adjunct to the apparatus of the 
chemist or the manufacturer, but as a means of 
innocent and instructive recreation, has become 
so firmly rooted amongst us that it seems hardly 
necessary to advocate its claims to attention on 
any of these grounds. 

So wonderful is the information which it affords, 
so indispensable is it in many, if not in all, 
branches of scientific research, that not only would 
the lover of nature be deprived of one of his most 
valued sources of information and enjoyment, but 



2 USES OF MICROSCOPY 

some sciences would be brought absolutely to a 
standstill if by any conceivable means the 
microscope were to be withdrawn from their 
followers. 

On the other hand, from every improvement in 
the construction of the latter, a corresponding en- 
largement and enlightenment of the fields reviewed 
by these sciences has taken place, and the beauty 
and interest of the revelations made by its means 
has attracted an ever-increasing host of earnest 
and intelligent volunteers, who have rendered 
yeoman service to the cause of knowledge. 

Moreover, so vast is the scope of the instrument, 
that whilst discoveries in other fields of research 
are few and far between, comparatively speaking, 
in microscopic science they are of everyday 
occurrence, and the number of problems calling 
for solution by means of the instrument in question 
is so vast that even the humblest worker may be 
of the greatest assistance. 

In the following pages we propose to carry out, 
as far as possible with reference to the microscope, 
the system followed in the " Common Objects of 
the Seashore and of the Country," and to treat in 
as simple a manner as may be of the marvellous 
structures which are found so profusely in our 
fields, woods, streams, shores, and gardens. More- 
over, our observations will be restricted to an 
instrument of such a class as to be inexpensively 
purchased and easily handled, and to those pieces 
of supplementary apparatus which can be extem- 
porised at small cost of money and ingenuity by 




L 



SCIENTIFIC TECHNOLOGY 3 

the observer himself, or obtained of the opticians 
fur a few shillings. 

With the same view, the descriptions will be 
given in language as simple and as free from 
technicalities as possible, though it must be 
remembered that for many of the organisms and 
structures which we shall have to describe there 
are none but scientific names ; and since, moreover, 
this little work is intended to furnish a stepping- 
stone between the very elements of microscopic 
science, and those higher developments of it which 
should be the aim of every worker, it would be 
unwise to attempt to invent commonplace appel- 
lations for the purpose of this book, and leave him 
to discover, when he came to consult works of 
reference in any particular subject, that his 
" simplified " knowledge had all to be unlearnt, 
and a new vocabulary acquired. Eather will it be 
our purpose to use correct terms, and explain them, 
as far as necessary, as we introduce them. 

The commencing microscopist is strongly recom- 
mended, whilst not confining his interest entirely 
to one branch of research or observation, to adopt 
some one as his particular province. 

The opportunities for discovery and original 
work, which are afforded by all alike, will be more 
readily appreciated and utilised by adopting such 
a plan than by a general and purposeless dis- 
tribution of effort. To mention one or two. The 
student of the fascinating field of pond-life will find 
new organisms awaiting description by the hundred, 
and of the old ones, life-histories to make out ; if 



♦ FIELDS OF STUDY 

he be attracted rather to the vegetable inhabitants 
of the same realm, the diatoms will furnish him 
with the opportunity of studying, and perhaps 
solving, the enigma of their spontaneous movement, 
and of watching their development. The smaller 
fungi, and indeed the larger ones too, will amply 
repay the closest and most laborious study of their 
habits of life and processes of development. Since 
the first edition of this work was published, the 
whole subject has been practically revolutionised, 
and more remains to be done than has yet been 
accomplished. 

In short, there is scarcely an organism, even of 
those best known and most studied, which is so 
completely exhausted that persevering investigation 
would reveal nothing new concerning it. 

There can be little doubt but that if any worker, 
with moderate instrumental means, but with an 
observant mind, were to set determinately to work 
at the study of the commonest weed or the most 
familiar insect, he, or she, would by patient labour 
accomplish work which would not only be of value 
to science, but would redound to the credit of the 
worker. 

Something like finality appears to have been 
reached, at least for tLc present, in the develop- 
ment of the microscope ; and whilst it is beyond 
the "scope of this work to treat of the refined and 
costly apparatus which is essential to useful work 
in certain departments of research, the result has, 
on the whole, been highly favourable to the worker 
of moderate means and ambitions, since lenses are 



EXTEMPORISED APPARATUS 5 

now accessible, at the cost of a few shillings, com- 
paratively speaking, which could not have been 
purchased at all when this work first appeared. 
It is with such appliances that we have here to 
deal. The worker whose finances are restricted 
must be contented to extemporise for himself many 
pieces of apparatus*, and will find pleasure and 
occupation in doing so. And let him remember, 
for his encouragement, that many such home-made 
appliances will fulfil their purpose quite as well as 
the imposing paraphernalia of glittering brass and 
glass which decorates the table of the wealthy 
amateur. It is not the man who possesses the 
best or most costly apparatus, but the one who 
best understands the use of that which he possesses, 
that will make the most successful microscopist. 
A good observer will discover, with only the aid of 
a pocket-magnifier, secrets of Nature which have 
escaped the notice of a whole army of dilettante 
microscopists, in spite of the advantages which, as 
regards instruments, the latter may enjoy. 

It is for those who desire to be of the former 
class that this book is written, and in the course 
of the following pages instances will be given in 
which the exercise of a small amount of ingenuity 
and the expenditure of a few pence will be found 
equivalent to the purchase of costly and complicated 
apparatus. 

An enormous amount of valuable work was done 
in the earliest days of microscopy, when the best 
apparatus available was a single lens, composed of 
the bead formed by fusing the drawn-out end of a 



6 SIMPLE MICROSCOPES 

rod of glass. Inserted into a plate of metal, or a 
piece of card, such a primitive instrument was 
capable of affording a large amount of information. 
Similar instruments are to be purchased for a few 
pence at the present day, and are not without their 
use for purposes of immediate examination of 
material. A very common form is a glass marble, 
ground flat on one side, and mounted in a tube. 
The material to be examined is placed upon the 
flat side, and is seen magnified to an extent 
inversely proportional to the diameter of the sphere 
of glass. 



CONVEX LENSES 



CHAPTER II 

Elementary Principles of Optics — Simple Microscopes — Com- 
pound Microscope — Accessory Apparatus — Cover-glasses 
— Troughs— Condensers — Dissection — Dipping- tubes — 
Drawing — Measurement. 

Before proceeding to deal with the microscope 
itself, it may be useful to give a short summary of 
the optical laws upon which its working depends. 

To go into the minutiae of the matter here would 
be out of place, but it will be found very helpful, 
especially in the matter of illumination, to acquire 
some knowledge of, and facility in applying, these 
elementary principles. We shall confine our 
remarks to convex lenses, as being the form to 
which all the combinations in the microscope may 
be ultimately reduced. 

Every convex lens has one " principal " focus, 
and an infinite number of " conjugate " foci. The 
principal focus is the distance at which it brings 
together in one point the rays which fall upon it 
parallel to its axis, as shown in Fig. 1, in which A 
is the axis of the lens L, and the rays BB are 
brought together in the principal focus P. Thus 
a ready means of finding the focal length of any 
lens is to see at what distance it forms an image 



8 CONJUGATE FOCI 

of the sun, or of any other distant object, upon a 
screen, such as a piece of smooth white cardboard. 
In the figure this distance will be PL. Conversely, 
if the source of light be at P, a parallel beam of 
light will be- emitted from the lens. 

The focal length may, however, be found in 
another way. When an object is placed at a 
distance from a lens equal to twice the principal 
focal length of the latter, an image of the object is 
formed at the same distance upon the other side of 




Fig. I. 

the lens, inverted in position, but of the same 
dimensions as the original object. The object and 
image then occupy the equal conjugate foci of the 
lens, so that by causing them to assume these 
relative positions, and halving the distance at 
which either of them is from the lens, the focal 
length of the latter is known. 

These points will be seen on reference to Fig. 2, 
in which L being the lens, and P the principal 
focus, as before, rays from the point G are brought 
together at the conjugate focus C', at the same 



FORMATION OF IMAGR 9 

distance on the other side of L. In this case it 
manifestly does not matter whether the object bo 
at one or the other of these points. 

So far we have been dealing with points on the 
line of the axis of the lens. The facts mentioned 
apply equally, however, to rays entering the lens 
at an angle to the axis, only that in this case they 
diverge or converge, correspondingly, upon the 
other side. It is evident, from Fig. 1, that no 
image is formed of a point situated at the distance 




Fio. 2. 

of the principal focus ; but Fig. 3, which is really 
an extension of Fig. 2, shows how the rays passing 
along secondary axes form "an inverted image of the 
same size as the object, when the latter is situated 
at twice the focal length of the lens from this last. 
To avoid confusion, the bounding lines only are 
shown, but similar lines might be drawn from each 
and every point of the object; and if the lines 
ALA', BL'B' be supposed to be balanced at L and 
L' respectively, they will indicate the points at 
which the corresponding parts of the object and 



to REAL IMAGE 

image will bo situated along the lines AB, B'A' 
respectively. Moreover, rays pass from every part 
of the object to every part of the lens, so that wo 
must imagine the cones LAL', LA'L' to be filled 
with rays diverging on one side of the lens and 
converging on the other. 

The image so formed is a " real " image, — that is 
to say, it can be thrown upon a screen. 

The microscopic image, on the other hand, is 
a virtual image, which can be viewed by the eye 
but cannot be thus projected, for it is formed by an 




Fro. 3. 

object placed nearer to the lens than the principal 
focal length of the latter, so that the rays diverge, 
instead of converging, as they leave the lens, and the 
eye looks, as it were, back along the path in which 
the rays appear to travel, and so sees an enlarged 
image situated in the air, farther away than the 
object, as shown in Fig. 4. In this case, as the 
diagram shows, the image is upright, not inverted. 

Images of the latter class are those formed by 
simple microscopes, of the kind described in the 
previous chapter. In the compound microscope 



VIRTUAL IMAGE 



It 



the initial image, formed by the object-glass, is 
further magnified by another set of lenses, forming 
the eye-piece, by which the diverging rays of the 
virtual image are brought together to a focus at 
the eye-point ; and when viewed directly, the eye 
sees an imaginary image, as in a simple microscope, 
whilst, when the rays are allowed to fall upon a 
screen, they form a real image of the object, larger 




Pic. 4. 



or smaller, as the screen is farther from or nearer 
to the eye-point. 

These remarks must suffice for our present 
purpose. Those who are sufficiently interested in 
the subject to desire to know more of the delicate 
corrections to which these broad principles are 
subjected in practice, that objectives may give 
images which are clear and free from colour, to say 
nothing of other faults, will do well to consult some 



12 A PLEA FOR LOW POWERS 

such work as Lomroel'a Optics, in the International 
Science Series. 

In following a work such as the present one, the 
simple microscope, in some form or other, will be 
found almost indispensable. It will be required 
for examining raw material, such as leaves or other 
parts of plants, for gatherings of life in fresh or 
salt water, for dissections. With such powers as 
those with which we shall have to deal, it will 
rarely happen that, for example, a bottle of water 
in which no life is visible will be worth the 
carrying-home ; whilst, on the other hand, a few 
months' practice will render it not only possible, 
but easy, not only to recognise the presence, but to 
identify the genus, and often even the species, of 
the forms of life present. Moreover, these low 
powers, affording a general view of the object, 
allow the relation to each other of the details 
revealed by the power of the compound microscope 
to be much more easily grasped. A rough example 
may suffice to illustrate this. A penny is a suffi- 
ciently evident object to the naked eye, but it will 
require a sharp one to follow the details in 
Britannia's shield, whilst the minute scratches 
or the bloom upon the surface would be invisible in 
detail without optical aid. Conversely, however, 
it would be rash to conclude from an examination 
of a portion of the surface with the microscope 
alone that the portion in view was a sample of the 
whole surface. The more the surface is magnified, 
the less are the details grasped as a whole, and for 
this reason the observer is strongly recommended 



PORTABLE APPARATUS 



n 




Fig. 5. 



to make out all that he can of an ohject with a 
simple magnifier before resorting to the microscope. 

For general purposes, the intending observer 
cannot do better than supply himself with a 
common pocket-magnifier, with one, two, or three 
lenses, preferably the last, as although the absolute 
performance is not so accurate, the very consider- 
able range of power available by using the lenses 
singly, or in various combinations, is of great 
advantage. Such a magnifier may be obtained 
from Baker for about three-and- 
sixpence, or, with the addition 
of a powerful Coddington lens 
(Fig. 5) in the same mount, for 
nine shillings more. Aplanatic 
lenses, such as the one shown in 
section in Fig. 6, with a much 
Hatter field of vision, but of one 
power only each, cost about 
fifteen shillings, and a simple 
stand, which adapts them for 
dissecting purposes, may be ob- 
tained of the same maker for half a crown, or may 
easily be extemporised from a cork sliding stiffly 
on an iron rod set in a heavy foot, the cork carry- 
ing a loop of wire terminating in a ring which 
carries the lens. 

So much may suffice for the simple microscope. 
We pass on now to the consideration of the instru- 
ment which forms the subject of the present work, 
an instrument which, whilst moderate in price, is 
yet capable of doing a large amount of useful and 




Fio. 6. 



H 



THE POPULAR MICROSCOPE 



valuable work in the hands of a careful owner, and 
of affording him a vast amount of pleasure and re- 
creation, even if these be his only objects in the 
purchase, though it is difficult to understand that, 
an insight being once attained into the revelations 
effected by the instrument, without a desire being 

excited in any intelli- 
gent mind to pursue 
the subject as a study 
as well as a delightful 
relaxation. The micro- 
scope described, and 
adopted as his text 
by the author of this 
work, is still made, 
and has shared to a 
very considerable ex- 
tent in the general 
improvement of optical 
apparatus which has 
taken place during the 
last thirty years. It 
is to be obtained from 
Baker, 244 High Hol- 
born, and is provided 
with most of the apparatus which will be found 
indispensable by the beginner, costing, with a case 
in which to keep it, the modest sum of three 
guineas. 

If this instrument represent the limit of the 
purchaser's power of purse, he may very well make 
it answer his purpose for a considerable time. The 




Fig. 7. 



A MORE COMPLETE FORM 



IS 



same instrument, however, with separate objectives 

of good quality, together with a bull's-eye condenser 

(an almost indispensable adjunct), a plane mirror in 

addition to a concave one, and a simple but efficient 

form of substage condenser, may be obtained for 

£5, 12s. 6d., 

and the extra 

outlay will be 

well repaid by 

the advantage 

in working 

which is 

gained by the 

possession of 

the additional 

apparatus. 

A still 
better stand, 
and one 
which is good 
enough for 
almost any 
class of work, 
is that shown 
in Fig. ' 8, 
which is 
known as the " Portable " microscope. In this 
instrument the body is made up of two tubes, so 
that the length may be varied at will, and this 
gives a very considerable range of magnification 
without changing the object-glass, a great con- 
venience in practice ; whilst the legs fold up 




Fig. 8. 



16 



COMBINATION OBJECTIVES 



for convenience of carriage, so that the whole 
instrument, with all necessary appliances, may 
be readily packed in a corner of a portmanteau for 
transport to the country or seaside. 

The objectives supplied with the simplest form of 
microscope above referred to are combinations of 
three powers in one, and the power is varied by 
using one, two, or three of these in combination. 
This form of objective is very good, as far as it 
goes, tbough it is impossible to correct such a com- 




<&s" 




Fig. 9. 

bination with the accuracy which is possible in 
manufacturing one of a fixed focal length. 

Perhaps the best thing for the beginner to do 
would be to purchase the combination first, and, 
later on, to dispose of it and buy separate objectives 
of, say, one-inch, half-inch, and quarter-inch focal 
lengths. It may be explained here, that when a 
lens is spoken of as having a certain focal length, 
it is meant that the magnification obtained by its 
use is the same, at a distance of ten inches from the 



L/1'E BOX 



'7 



eye, as would be obtained by using a simple sphere 
of glass of the same focal length at the same 
distance. This, of course, is simply a matter of 
theory, for such lenses are never used actually. 

Of accessory apparatus, we may mention first the 
stage forceps (Fig. 9, a). These are made to fit into 
a hole upon the stage, so as to be capable of being 
turned about in any direction, with an object in 
their grasp, and for some purposes, especially such 
as the examination of a thin object, say the edge of 
a leaf, they are ex- 
tremely useful. 

The live box, 
in which drops of 
water or portions 
of water-plants, or 
the like, may be 
examined, will be 
found of great C 
service. By ad- 
justment of the 

cap upon the cylinder, with proper attention to the 
thickness of the cover-glass in the cap, any required 
amount of pressure, from that merely sufficient to 
fix a restless object to an amount sufficient to crush 
a resistent tissue, may easily be applied, whilst the 
result of the operation is watched through the 
microscope. This proceeding is greatly facilitated 
if the cap of the live-box be slotted spirally, with a 
stud on the cylinder, so that a half-turn of the cap 
brings the glasses into contact. By this means the 
pressure may be adjusted with the greatest nicety. 




Fig. 10. 



1 8 SLIDES AND COVERS 

In examining delicate objects, such as large in- 
fusoria, which invariably commit suicide when 
pressure is applied, a good plan is to restrict their 
movements by placing a few threads of cotton-wool, 
well pulled out, in the live-box with the drop of 
water. 

A variety of instruments has been invented for 
the same purpose, of which Beck's parallel com- 
pressorium may be mentioned as the most efficient, 
though it is somewhat complicated, and consequently 
expensive, costing about twenty-five shillings. 

A few glass slips and cover-glasses will also be 
required. The latter had better be those known as 
" No. 2," since the beginner will find it almost 
impossible to clean the thinner ones satisfactorily 
without a large percentage of fractures. The safest 
way is to boil the thin glass circles in dilute nitric 
acid (half acid, half water) for a few minutes, wash 
well in several waters, first tap-water and then dis- 
tilled, and finally to place the covers in methylated 
spirit. When required for use, the spirit may be 
burnt off by applying a light, the cover-glass, held 
in a pair of forceps, being in no way injured by the 
process. 

In addition to the glass slides, the observer will 
find it advisable to be provided with a few glass 
troughs, of various thicknesses, in which portions of 
water-plants, having organisms attached to them, 
may be examined. Confined in the live-box, many 
of the organisms ordinarily found under such circum- 
stances can rarely be induced to unfold their beauties, 
whilst in the comparative freedom of the trough 



GLASS TROUGHS 19 

they do so readily. The troughs may be purchased, 
or may be made of any desired shape or size by 
cutting strips of glass of a thickness corresponding 
to the depth desired, cementing these to a glass 
slide somewhat larger than the ordinary one, and 
cementing over the frame so formed a piece of thin 
glass, No. 3 ; the best material to use as cement 
being marine glue of the best quality, or, failing 
this, Prout's elastic glue, which is much cheaper, 
but also less satisfactory. The glass surface must 
be made, in either case, sufficiently hot to ensure 
thorough adhesion of the cement, as the use of any 
solvent entails long waiting, and considerable risk 
of poisoning the organisms. A useful practical 
hint in the use of these troughs is that the corners, 
at the top, should be greased slightly, otherwise the 
water finds its way out by capillary attraction, 
to the detriment of the stage of the microscope. 

Of optical accessories, the bull's-eye is almost the 
most valuable. So much may be effected by its 
means alone, in practised hands, that it is well 
worth the while of the beginner to master its use 
thoroughly, and the methods of doing so will be 
explained in the succeeding chapter. 

The substage condenser, too, even in its most 
simple form, is an invaluable adjunct, even though 
it be only a hemisphere of glass, half an inch or so 
in diameter, mounted in a rough sliding jacket to fit 
underneath the stage. Such an instrument, properly 
fitted, will cost about fifteen shillings, but the in- 
genious worker will easily extemporise one for 
himself. 



20 



DISSECTION 



Many plants and animals require to be dissected 
to a certain extent before the details of their struc- 
ture can be made out, and for this purpose the 
naked eye alone will rarely serve. The ordinary 
pocket magnifier, however, if mounted as described 
in a preceding chapter, will greatly facilitate matters, 
and the light may be focused upon the object by 
means of the bull's-eye condenser, as shown in 




M e i 




Via, 11. 



Fig. 11. In the figure the latter is represented 
as used in conjunction with the lamp, but daylight 
is preferable if ifc be available, the strain upon the 
eyes being very much less than with artificial light. 
Two blocks of woo J, about four inches high, will 
form convenient rests for the hands, a plate of glass 
being placed upon the blocks to support the dish, 
and a mirror being put in the interspace at an angle 
of 45° or so if required. A piece of black paper 



DISSECTING MEDIA 21 

may be laid upon the mirror if reflected light alone 
is to be used. 

As all delicate structures are dissected under fluid, 
a shallow dish is required. For this purpose nothing 
is better than one of the dishes used for develop- 
ing photographic negatives. The bottom of the dish 
is occupied by a flat cork, to which a piece of flat 
lead is attached below, and the object having been 
pinned on to the cork in the required position, the 
fluid is carefully run in. This fluid will naturally 
vary according to the results desired to be obtained, 
but it must not be plain water, which so alters all 
cellular structures as to practically make them un- 
recognisable under the microscope. Nothing could 
be better than a 5 per cent, solution of formalin, 
were it not for the somewhat irritating odour of 
this fluid, since it at once fixes the cells and pre- 
serves the figure. For many purposes a solution of 
salt, in the proportion of a saltspoonful of the 
latter to a pint of water, will answer well for short 
dissections. Tor more prolonged ones, a mixture of 
spirit-and-water, one part of the former to two of 
the latter, answers well, especially for vegetable 
structures. When the dilution is first made, the 
fluid becomes milky, unless pure spirit be used, but 
with a little trouble the Eevenue authorities may 
be induced to give permission for the use of pure 
methylated spirit, which answers every purpose. The 
trouble then is that not less than five gallons can be 
purchased, an embarras de richesses for the average 
microscopist, but, after all, the spirit is extremely 
cheap, and does not deteriorate by keeping. 



22 DISSECTING APPARATUS 

When the dissection in either of these media is 
completed, spirit should he gradually added to 
bring the strength up to 50 per cent., in which 
the preparation may remain for a day or two, after 
which it is gradually brought into pure spirit, or 
into water again, according to the medium in which 
it is to be mounted. 

As to the tools required, they are neither 
numerous nor expensive. Fine-pointed but strong 
forceps (Fig. 9, c), curved and straight; a couple of 
pairs of scissors, one strong and straight, the other 
more delicate, and having curved blades, and a few 
needles of various thicknesses and curves, are the 
chief ones. The latter may be made by inserting 
ordinary needles, for three-fourths of their length, 
into sticks of straight-grained deal (ordinary fire- 
wood answers best), and thereafter bending them 
as required. A better plan, however, is to be 
provided with a few of the needle-holders shown 
in Fig. 9, h. These are very simple and inex- 
pensive, and in them broken needles are readily 
replaced by others. Dipping-tubes, such as are 
shown in Fig. 12, will also be extremely useful 
for many purposes. These are very easily made 
by heating the centre of a piece of soft glass 
tubing of the required size, and, when it is quite 
red-hot, drawing the ends apart. The fine tube 
in the centre should now be divided by scratching 
it with a fine triangular file, and the scratch may 
of course be made at such a point as to afford a 
tube of the required fineness. The edges should 
be smoothed by holding them in the flame until 



DIPPING TUBES 



23 



they just run (not melt, or the tube will close). 
These tubes can often be made to supply the place 
of a glass syringe. They may be used either for 
sucking up fluid or for transferring it, placing the 
finger over the wide end, allowing the tube to fill 





Fig. 12. 



by displacement of air, and then re-closing it with 
the finger. This last method is especially useful 
for transferring small objects from one receptacle 
to another. In speaking of the dissection of 
objects, it should have been mentioned that the 
microscope itself may, under careful handling, be 



24 



ERECTING PRISM 



made to serve very well, only, as the image is 
reversed, it is almost impossible to work without 
using a prism to re -erect the image. Such a 
prism is shown in Fig. 13. The microscope is 
placed vertically, and the observer, looking straight 
into the prism, sees all the parts of the image 
in their natural positions. This appliance is 
extremely useful for the purpose of selecting 
small objects, and arranging them on slides in 




Fio. 13. 



any desired manner. A few words may be added 
as to the reproduction of the images of objects. 
The beginner is strongly recommended to 
practise himself in this from the outset. Even 
a rough sketch is worth pages of description, 
especially if the magnification used be appended ; 
and even though the worker may be devoid of 
artistic talent, he will find that with practice he 
will acquire a very considerable amount of facility 
in giving truthful outlines at least of the objects 



DRAWING APPLIANCES 25 

winch he views. Various aids have been devised 
for the purpose of assisting in the process. The 
simplest and cheapest of these consists of a cork 
cut so as to fit round the eye-piece. Into the 
cork are stuck two pins, at an angle of 45° to 
the plane of the cork, and, the microscope being 
placed horizontally, a thin cover-glass is placed 
upon the two pins, the light being arranged and 
the object focused after the microscope is inclined. 
On looking vertically down upon the cover-glass, 
a bright spot of light will be seen, and as the eye 
is brought down into close proximity with it the 
spot will expand and allow the observer to see 
the whole of the image without looking into the 
microscope. If a sheet of paper be now placed 
upon the table at the place occupied by the image 
so projected, the whole of the details will be 
clearly seen, as will also the point of a pencil 
placed upon the paper in the centre of the field 
of view ; and, after a little practice, it will be 
found easy to trace round the chief details of the 
object. Two points require attention. The first 
is that if the light upon the paper be stronger 
than that in the apparent field of the microscope, 
the image will not be well seen, or if the paper be 
too feebly lighted, it will be difficult to keep the 
point of the pencil in- view. The light from the 
microscope is thrown into the eye, and the view 
of the image upon the paper is the effect of a 
mental act, the eye looking out in the direction 
from which the rays appear to come. The paper 
has therefore to be illuminated independently, and 



26 REFLECTORS FOR DRAWING 

half the battle lies in the adjustment of the 
relative brightness of image and paper. The 
second point is, that it is essential to fix one 
particular point in the image as the starting-point 
of the drawing, and this being first depicted, the 
image and drawing of this point must be kept 
always coincident, or the drawing will be distorted, 
since the smallest movement of the eye alters the 
relations of the whole. The reflector must be 
placed at an angle of 45°, or the field will be 
oval instead of circular. The simple form of 
apparatus just described has one drawback, inas- 
much as the reflection is double, the front and 
back of the cover-glass both acting as reflectors. 
The image from the latter being much the more 
feeble of the two, care in illumination will do 
much to eliminate this difficulty; but there are 
various other forms in which the defect in 
question is got rid of. The present writer has 
worked with all of them, from the simple neutral 
tint reflector of Beale to the elaborate and costly 
apparatus of Zeiss, and, upon the whole, thinks 
that he prefers the cover-glass to them all. 

A very simple plan, not so mechanical as the 
last-named, consists in the use of " drawing- 
squares," which are delicate lines ruled upon a 
piece of thin glass, and -dropped into the eye- 
piece so that the lines rest upon the diaphragm 
of the eye-piece, and therefore are in focus at the 
same time as the object. By the use of these, 
ia combination with paper similarly ruled, a 
diagram of any required size can be drawn with 



MA GNIFICA T10N 27 

very great facility. The squares, if compared with 
a micrometer, will furnish an exact standard of 
magnitude for each object-glass employed. The 
micrometer is a piece of thin glass upon which 
are ruled minute divisions of an inch or a milli- 
meter. Suppose the micrometer to be placed 
under the microscope when the squares are in 
the eye-piece, and it be found that each division 
corresponds with one square of the latter, then, 
if the micrometric division be one one-hundredth 
of an inch, and the squares upon the paper 
measure one inch, it is clear that the drawing 
will represent the object magnified a hundred 
" diameters " ; if two divisions of the micrometer 
correspond to three squares, the amplification will 
be a hundred and fifty diameters ; if three divisions 
correspond to two squares, sixty-six diameters, and 
so on. If a draw- tube be used, it will be necessary 
to know the value of the squares at each inch of 
the length, if they are to be used for measuring 
magnification. 



USE OF THE MICROSCOPE 



CHAPTER III 

Examination of Objects — Principles of Illumination — Mirror 
and its Action — Substage Condenser — Use of Bull's-eye 
— Opaque Objects — Photography of Microscopic Objects. 

So much depends upon a right method of employ- 
ing the microscope, as regards both comfort and 
accuracy, that we propose to devote a little space 
to the consideration of the subject. 

Let us first warn the intending observer against 
the use of powers higher than are required to 
bring out the details of the object. Mere magni- 
fication is of very little use : it increases the 
difficulties both of illumination and of manipula- 
tion, and, as already said, interferes with that 
grasp of the object which it is most desirable 
to obtain. Bather let the beginner lay himself 
out to get the very most he can out of his 
lowest powers, and he will find that, by so doing, 
he will be able far better to avail himself of the 
higher ones when their use is indispensable. 

The essential means to this end is a mastery of 
the principles of illumination, which we now pro- 
ceed to describe. 

We suppose the microscope to be inclined at 
an angle of about 70° to the horizontal, with a 



METHODS OF ILLUMINATION 29 

low-power objective attached to it, a one-inch by 
preference. Opposite to the microscope, and about 
a foot away from it, is a lamp with the edge of 
the flame presented to the microscope, the concave 
mirror of which is so arranged as to receive the 
rays from the flame and direct them up the tube 
of the microscope. Upon the stage is placed a 
piece of ground-glass, and the mirror-arm is now 
to be moved up or down upon its support until the 
ground-glass receives the maximum of illumination, 
which it will do when the lamp-flame is at one 
conjugate focus of the mirror and the ground-glass 
at the other. The focus will not be an image of 
the flame, but a bar of light. 

If an object be now placed upon the stage, 
instead of the ground-glass, and the objective 
focused upon it, it will, if the mirror be properly 
adjusted, be brilliantly illuminated. 

It will be understood that every concave mirror 
has a focus, and converges the rays which fall upon 
it to this focus, behaving exactly like a convex 
lens. The principal focus of a concave mirror is 
its radius of curvature, and this is not difficult to 
determine. Place side by side a deep cardboard 
box and the lamp, so that the concave mirror may 
send the rays back, along a path only slightly 
inclined to that by which they reached it, to the 
bottom of the box. The lamp and box being 
equidistant from the mirror, it is evident that 
when the mirror forms an image of the former 
upon the latter equal to the flame in size, we 
have the equivalent of the equal conjugate foci 



30 MEASUREMENTS OF FOCUS 

shown in Fig. 2. Now move the box to the 
distance from the mirror which corresponds to 
the distance of the stage of the microscope from 
the mirror when the latter is in position upon 
the microscope, and then move the lamp to or 
fro until the mirror casts a sharp image of the 
flame upon the bottom of the box, which is not 
to be moved. The lamp distance so found will be 
the correct one for working with the concave 
mirror. The writer is led to lay special stress 
upon this matter, from the fact that he almost 
invariably finds that the mirror is arranged to be 
used for parallel rays, i.e. for daylight, and is 
therefore fixed far too close to the stage to be 
available for correct or advantageous working with 
the lamp, unless, indeed, the bull's-eye condenser 
be used, as hereinafter described, to parallelise the 
rays from the lamp. 

Work done with the concave mirror can, how- 
ever, under the most favourable conditions, only 
be looked upon as a pis alter. The advantages 
gained by the use of some substage condenser, 
even the most simple, in conjunction with the plane 
mirror, or even without any mirror at all, are so 
manifold that the beginner is strongly urged to 
provide himself with some form or other of it, 
and we now proceed to describe the way in which 
this should be used to produce the best effect. 

To reduce the problem to its most simple 
elements, turn the mirror altogether out of the 
way, and place the microscope upon a block at 
such a height as shall be convenient for obscrva- 



PROPER ARRANGEMENT OF LIGHT 31 

tion, and shall allow the rays from the lamp, 
placed in a line with it on the table, to shine 
directly into the tube of the microscope. Ascertain 
that this is so by removing both objective and 
eye-piece and looking down the tube, when the 
flame should be seen in the centre, edgewise. 
Now replace the eye-piece, and screw on to the 
tube the one-inch combination or objective. Place 
upon the stage an object, preferably a round diatom 
or an echinus-spine, and focus it as sharply as 
possible. Now place the substage condenser in its 
jacket, and slide it up and down until the image of 
the object is bisected by the image of the flame. 

The centre of the object will now be brilliantly 
illuminated by rays travelling in the proper direc- 
tion for yielding the best results. The object is 
situated at the common focus of the microscope and 
the condenser, and, whatever means of illumination 
be adopted, this is the result which should always 
be aimed at. 

Satisfactory as this critical arrangement is, how- 
ever, from a scientific point of view, it has its 
drawbacks from an artistic and sesthetic one. It 
is not pleasant, for most purposes, to have merely 
the centre of an object lighted up, and we have 
now to consider how the image of the edge of 
the flame may be so expanded as to fill the field 
without sacrificing more than a very small fraction 
of the accuracy of the arrangement just attained. 

Eef erring to Fig. 1, we see that if we place 
the lamp at the principal focus of a lens, it will 
emit a bundle of parallel rays equal in diameter 



32 USE OF THE "BULL'S-EYE" 

to the diameter of the lens. This is the key of 
the position. We cannot place the lamp at an 
infinite distance from the substage condenser, but 
we can supply the latter with rays approximately 
parallel, so that it shall bring them to a focus upon 
the object at very nearly its own principal focus. 
This we do by means of the bull's-eye condenser. 
Place the latter, with its flat side toward the edge 
of the flame, and at its principal focal distance 
(the method of determining which has already 
been described) from the latter, so that the bundle 
of parallel rays which issue from it may pass up 
to the substage condenser. On examining the 
object again, it will be found that, after slight 
adjustments of the position of the bull's-eye have 
been made, the object lies in the centre of an 
evenly and brilliantly lighted field. 

It may be necessary to place the bull's-eye a 
little farther from or nearer to the lamp, or to 
move it a little to one side or the other, but when 
it is at the correct distance, and on the central 
line between the lamp and the substage condenser, 
at right angles to this line, the effects will be as 
described. It may help in securing this result if 
we mention that when the bull's-eye is too far 
from the lamp, the image of the flame is a spindle- 
shaped one ; whilst, when the distance between the 
two is too short, i.e. less than the principal focal 
length of the lens, the field is crossed by a bar 
or light, the ends of which are joined by a ring, 
whilst on either side of the bar there is a semi- 
circular dark space. 



OPAQUE OBJECTS 33 

We have hitherto supposed the objects viewed 
to be transparent, bixt there are many, of great 
interest, which are opaque, and call for other 
means of illumination. Of these there are several. 
The simplest and, in many ways, the best is to 
use the bull's-eye condenser to bring to a focus 
upon the object the rays of light from some source 
placed above the stage of the microscope. If light 
can be obtained from the sun itself, no lens will 
be needed to concentrate it ; and indeed, if this 
were done, there would be considerable risk of 
burning the object. The light from a white 
cloud, however, with the help of the bull's-eye, 
answers admirably. At night-time an artificial 
source of light, the more intense and the more 
distant the better, is required. Tor most cases, 
and with powers not higher than one inch, a good 
paraffin lamp, placed about two feet away from the 
stage, and on one side of it, so as to be about a 
foot above the level of the object, will give all 
that is needed. Such a lamp is shown in Fig. 14. 
Low magnifications are, as a rule, all that is called 
for in this method. 

Lieberkuhn's condensers are useful aids, but are 
somewhat expensive. They are concave mirrors, 
which are so adjusted to the objective that the 
latter and the reflector come into focus together, 
the light being sent in from below, or from one side. 

One other method of illumination must be men- 
tioned before leaving the topic, and this is the 
illumination of objects upon a " dark field." With 
suitable subjects, and when carefully managed;. 
3 



34 



ILLUMINATION ON 



there is no method which gives more beautiful 
effects, and it has the great advantage of allowing 
the object to be brilliantly lighted, without the 
strain to the eyes which is involved in such light- 
ing by the usual method of direct illumination. 




Fig. 14. 



It consists essentially in allowing the light to 
fall upon the object from below, at such an angle 
that none of it can enter the objective directly. 
Thus the concave mirror, turned as far as possible 
to one side, and reflecting on to the object the rays 
from the lamp placed upon the opposite side, will 



A DARK BACKGROUND 35 

give very fair results with low powers ; this plan, 
however, is capable of but very limited application. 
Again, a disc of black paper may be stuck on to 
the middle of the bull's-eye, and the latter be 
placed below the stage between it and the mirror. 
In this case everything depends upon the size of 
the disc, which, if too small, will not give a black 
ground, and if too large will cut off all light from 
the object. 

The best and only really satisfactory plan is to 
arrange the illumination with trie substage con- 
denser, as previously described, and then to place 
below the lens of the latter a central stop of a 
suitable size, which can only be determined by 
trial. When this has been done the object will 
be seen brilliantly illuminated upon a field of 
velvety blackness. Such stops are supplied with 
the condenser. 

We have devoted a considerable portion of space 
to this question, since it is, of all others, the most 
important to a successful, satisfactory, and reliable 
manipulation of the microscope ; but even now, only 
the main points of the subject have been touched 
upon, and the worker will find it necessary to, 
supplement the information given by actual ex- 
periment. A few failures, rightly considered, will 
afford a great amount of information, but those 
who desire to go thoroughly into the matter are 
recommended to consult the present writer's Guide 
to the Science of Photomicrography, where it is 
treated at much greater length, as an essential 
part of the subject-matter of the book. 



j6 PHOTOGRAPHING OBJECTS 

It may be added here, that no method of repro- 
ducing the images of objects is on the whole so 
satisfactory as the photographic one ; and whilst a 
lengthened reference to the topic would be out of 
place in a work of the character of the present one, 
the one just mentioned will be found to contain all 
that is necessary to enable the beginner to produce 
results which, for faithfulness and beauty, far excel 
any drawing, whilst they have the additional ad- 
vantage that they can, if required, be exhibited to 
hundreds simultaneously. 



CEMERAL COUNSELS 37 



CHAPTER IV 

Wgi'hihle Cells and their Structure — Stellate Tissues — 
Secondary Deposit — Ducts and Vessels — Wood-Cells — 
Stornata, or Mouths of Plants — The Camera Lucida, and 
Mode of Using — Spiral and Ringed Vessels — Hairs of 
Plants— Tiesins, Scents, and Oils — Bark Cells. 

"We will now suppose the young observer to have 
obtained a microscope and learned the use of its 
various parts, and will proceed to work with it. 
As with one or two exceptions, which are only 
given for the purpose of further illustrating some 
curious structure, the whole of the objects figured 
in this work can be obtained without any diffi- 
culty, the best plan will be for the reader to procure 
the plants, insects, etc., from which the objects are 
taken, and follow the book with the microscope at 
hand. It is by far the best mode of obtaining a 
systematic knowledge of the matter, as the quantity 
of objects which can be placed under a microscope is 
so vast that, without some guide, the tyro flounders 
hopelessly in the sea of unknown mysteries, and 
often becomes so bewildered that he gives up the 
study in despair of ever gaining any true knowledge 
of it. I would therefore recommend the reader to 
work out the subjects which are here mentioned 



3? VEGETABLE CELLS 

and [hen to launch out for himself on the voyage 
of discovery. I speak from experience, having 
myself known the difficulties under which a young 
and inexperienced observer has to labour in so wide 
a field, without any guide to help him to set about 
his work in a systematic manner. 

The objects thai/ can be most; easily obtained are 
those of a vegetable nature, as even in London 
there is not a square, an old wall, a greenhouse, a 
florist's window, or even a greengrocer's shop, that 
will not afford an exhaustless supply of microscopic 
employment. Even the humble vegetables that 
make their daily appearance on the dinner-table 
are highly interesting ; and in a crumb of potato, a 
morsel of greens, or a fragment of carrot, the enthus- 
iastic observer will find occupation for many hours. 

Following the best examples, we will commence at 
the beginning, and see how the vegetable structure is 
built up of tiny particles, technically called " cells." 

That the various portions of every vegetable 
should be referred to the simple cell is a matter of 
some surprise to one who has had no opportunity 
of examining the vegetable structure, and indeed it 
does seem more than remarkable that the tough, 
coarse bark, the hard wood, the soft pith, the green 
leaves, the delicate flowers, the almost invisible 
hairs, and the pulpy fruit, should all start from 
the same point, and owe their origin to the simple 
vegetable cell. This, however, is the case ; and by 
means of a few objects chosen from different 
portions of the vegetable kingdom, we shall obtain 
Borne definite idea of this curious phenomenon. 



POJiM OF CELLS 39 

On l'late I. Fig. 1, miiy lie seen three cells of a 
somewhat globular form, taken from the common 
strawberry. Any one wishing to examine these 
cells for himself may readily do so by cutting a 
very thin slice from the fruit, putting it on a slide, 
covering it with a piece of thin glass (which may 
be cheaply bought at the optician's, together with 
the glass slides on which the objects are laid), and 
placing it under a power of two hundred diameters. 
Should the slice be rather too thick, it may be 
placed in the live-box and well squeezed, when the 
cells will exhibit their forms very distinctly. In 
their primary form the cells seem to be spherical ; 
but as in many cases they are pressed together, and 
in others are formed simply by the process of sub- 
division, the spherical form is not very often seen. 
The strawberry, being a soft and pulpy fruit, 
permits the cells to assume a tolerably regular 
form, and they consequently are more or less 
globular. 

Where the cells are of nearly equal size, and are 
subjected to equal pressure in every direction, they 
force each other into twelve-sided figures, having 
the appearance under the microscope of flat six- 
sided forms. Fig. 8, in the same Plate, taken from 
the stem of a lily, is a good example of this form 
of cell, and many others may be found in various 
familiar objects. 

We must here pause for a moment to define a 
cell before we proceed further. 

The cell is a close sac or bag formed of a 
substance called from its function " cellulose," and 



40 STRUCTURE OF CELLS 

containing certain semi-fluid contents as long as it 
retains its life. In the interior of the cell may 
generally be found a little dark spot, termed the 
" nucleus," and which may be seen in Fig 1, to 
which we have already referred. The object of the 
nucleus is rather a bone of contention among the 
learned, but the best authorities on this subject 
consider it to be the vital centre of the cells, to and 
from which tends the circulation of the protoplasm, 
and which is intimately connected with the growth 
and reproduction of the cell. On looking a little 
more closely at the nucleus, we shall find it marked 
with several small light spots, which are termed 
" nucleoli." 

On the same Plate (Fig. 2) is a pretty group of 
cells taken from the internal layer of the buttercup 
leaf, and chosen because they exhibit the series of 
tiny and brilliant green dots to which the colour 
of the leaf is due. The technical name for this 
substance is " chlorophyll," or " leaf -green," and it 
may always be found thus dotted in the leaves of 
different plants, the dots being very variable in size, 
number, and arrangement. A very fine object for 
the exhibition of this point is the leaf of Andcharis, 
the " Canadian timber-weed," to be found in almost 
every brook and river. It also shows admirably 
the circulation of the protoplasm in the cell. 

In the centre of the same Plate (Fig. 12) is a 
group of cells from the pith of the elder-tree. 
This specimen is notable for the number of little 
" pits " which may be seen scattered across the 
walls of the cells, and which resemble holes when 



STELLATE TISSUE 41 

placed under the microscope. In order to test the 
truth of this appearance, the specimen was coloured 
blue by the action of iodine and dilute sulphuric 
acid, when it was found that the blue tint spread 
over the pits as well as the cell-walls, showing 
that the membrane is continuous over the pits. 

Fig. 7 exhibits another form of cell, taken from 
the Spurganium, or bur-reed. These cells are 
tolerably equal in size, and have assumed a square 
shape. They are obtained from the lower part of 
the leaf. The reader who has any knowledge of 
entomology will not fail to observe the similarity 
in form between the six-sided and square cells of 
plants and the hexagonal and square facets of the 
compound eyes of insects and crustaceans. In a 
future page these will be separately described. 

Sometimes the cells take most singular and un- 
expected shapes, several examples of which will be 
briefly noticed. 

In certain loosely made tissues, such as are 
found in the rushes and similar plants, the walls of 
the cells grow very irregularly, so that they push 
out a number of arms which meet each other in 
every direction, and assume the peculiar form which 
is termed " stellate," or star-shaped tissue. Fig. 3 
shows a specimen of stellate tissue taken from the 
seed-coat of the privet, and rather deeply coloured, 
exhibiting clearly the beautiful manner in which 
the arms of the various stars meet each other. A 
smaller group of stellate cells taken from the stem 
of a large rush, and exemplifying the peculiarities 
of the structure, are seen in Fig 4. 



42 ELONGATED CELLS 

The reader will at once see that this mode of 
formation leaves a vast number of interstices, and 
gives great strengtli with little expenditure of 
material. In water-plants, such as the reeds, this 
property is extremely valuable, as they must be 
greatly lighter than the water in which they live 
and at the same time must be endowed with 
considerable strength in order to resist its 
pressure. 

A less marked example of stellate tissue is 
given in Fig. 11, where the cells are extremely 
irregular in their form, and do not coalesce 
throughout. This specimen is taken from the 
pithy part of a bulrush. There are very many 
other plants from which the stellate cells may 
be obtained, among which the orange affords very 
good examples, in the so-called " white " that lies 
under the yellow rind, a section of which may 
be made with a very sharp razor, and placed in 
the field of the microscope. 

Looking toward the bottom of the Plate, and 
referring to Fig. 27, the reader will observe a 
series of nine elongated cells, placed end to end, 
and dotted profusely with chlorophyll. These 
are obtained from the stalk of the common 
chickweed. Another example of the elongated 
cell is seen in Fig. 14, which is a magnified 
representation of the rootlets of wheat. Here 
the cells will be seen set end to end, and each 
containing its nucleus. On the left hand of the 
rootlet (Fig. 13) is a group of cells taken from 
the lowest part of the stem of a wheat plant 



PITTED CELLS 43 

which had hecu watered with a solution of 
carmine, and had taken up a considerahlo amount 
of the colouring substance. Many experiments 
on this subject were made by the Rev. Lord 
S. G. Osborne, and may be seen at full length 
in the pages of the Microscopical Journal, the 
subject being too large to receive proper treatment 
in the very limited space which can here be 
given to it. It must be added that later 
researches have caused the results here described 
to be gravely disputed. 

Fig. 9 on the same Plate exhibits two notable 
peculiarities — the irregularity of the cells and 
the copiously pitted deposit with which they are 
covered. The irregularity of the cells is mostly 
produced by the way in which the multiplication 
takes place, namely, by division of the original 
cell into two or more new ones, so that each of 
these takes the shape which it assumed when a 
component part of the parent cell. In this case 
the cells are necessarily very irregular, and when 
they are compressed from all sides they form 
solid figures of many sides, which, when cut 
through, present a flat surface marked with a 
variety of irregular outlines. This specimen is 
taken from the rind of a gourd. 

The " pitted " structure which is so well shown 
in this figure is caused by a layer of matter 
which is deposited in the cell and thickens its 
walls, and which is perforated with a number of 
very minute holes called " pits." This substance 
is called " secondary deposit." That these pits do 



44 SECONDARY DEPOSIT 

not extend through the real cell-w;ill has already 
been shown in Fig. 12. 

This secondary deposit assumes various forms. 
In some eases it is deposited in rings round the 
cell, and is clearly placed there for the purpose of 
strengthening the general structure. Such an 
example may be found in the mistletoe (Fig. 5), 
where the secondary deposit has formed itself 
into clear and bold rings that evidently give 
considerable strength to the delicate walls which 
they support. Fig. 10 shows another good instance 
of similar structure ; differing from the preceding 
specimen in being much longer and containing a 
greater number of rings. This object is taken 
from an anther of the narcissus. Among the 
many plants from which similar objects may be 
obtained, the yew is perhaps one of the most 
prolific, as ringed wood-cells are abundant in its 
formation, and probably aid greatly in giving to 
the wood the strength and elasticity which have 
long made it so valuable in the manufacture of 
bows. 

Before taking leave of the cells and their 
remarkable forms, we will just notice one example 
which has been drawn in Fig. 6. This is a 
congeries of cells, containing their nuclei, starting 
originally end to end, but swelling and dividing 
at the top. This is a very young group of cells 
(a young hair, in fact) from the inner part of a 
lilac bud, and is here introduced for the purpose 
of showing the great similarity of all vegetable 
cells in their earliest stages of existence. 



DUCTS AND VESSELS 45 

Having now examined the principal forms of 
cells, we arrive at the " vessels," a term which is 
applied to those long and delicate tubes which are 
formed of a number of cells set end to end, their 
walls of separation being absorbed. 

In Fi". 19 the reader will find a curious 
example of the " pitted vessel," so called from the 
multitude of little markings which cover its walls, 
and are arranged in a spiral order. Like the pits 
and rings already mentioned, the dots are composed 
of secondary deposit in the interior of the tube, 
and vary very greatly in number, function, and 
dimensions. This example is taken from the wood 
of the willow, and is remarkable for the extreme 
closeness with which the dots are packed together. 

Immediately on the right hand of the preceding 
figure may be seen another example of a dotted 
vessel (Fig. 20), taken from a wheat stem. In 
this instance the cells are not nearly so long, but 
are wider than in the preceding example, and are 
marked in much the same way with a spiral series 
of dots. About the middle of the topmost cell is 
shown the short branch by which it communicates 
with the neighbouring vessel. 

Fig. 2 3 exhibits a vessel taken from the common 
carrot, in which the secondary deposit is placed in 
such a manner as to resemble a net of irregular 
meshes wrapped tightly round the vessel. For 
this reason it is termed a " netted vessel." A very 
curious instance of these structures is given in 
Fig. 26, at the bottom of the Plate, where are 
represented two small vessels from the wood of the 



46 SCALARIFORM VESSELS 

elm. One of them — that on the left hand — is 
wholly marked with spiral deposit, the turns being 
complete ; while, in the other instance, the spiral 
is comparatively imperfect, and the cell-walls are 
marked with pits. If the reader would like to 
examine these structures more attentively, he will 
find plenty of them in many familiar garden 
vegetables, such as the common radish, which is 
very prolific in these interesting portions of veget- 
able nature. 

There is another remarkable form in which this 
secondary deposit is sometimes arranged that is 
well worthy of our notice. An example of this 
structure is given in Fig. 18, taken from the stalk 
of the common fern or brake. It is also found 
in very great perfection in the vine. On in- 
specting the illustration, the reader will observe 
that the deposit is arranged in successive bars 
or steps, like those of a winding staircase. In 
allusion to the ladder like appearance of this 
formation, it is called " scalariform " (Latin, scala, 
a ladder). 

In the wood of the yew, to which allusion has 
already been made, there is a very peculiar struc- 
ture, a series of pits found only in those trees that 
bear cones, and therefore termed the coniferous 
pitted structure. Fig. 1 6 is a section of a common 
cedar pencil, the wood, however, not being that of 
the true cedar, but of a species of fragrant Juniper. 
This specimen shows the peculiar formation which 
has just been mentioned. 

Any piece of deal or pine will exhibit the same 



CONIFEROUS CELLS 47 

peculiarities in a very marked manner, as is seen in 
Fig. 24. A specimen may be readily obtained by 
making a very thin shaving with a sharp plane. 
In tli is example the deposit has taken a partially 
spiral form, and the numerous circular pits with 
which it is marked are only in single rows. In 
several other specimens of coniferous woods, such 
as the Araucaria, or Norfolk Island pine, there are 
two or three rows .of pits. 

A peculiarly elegant example of this spiral deposit 
may be seen in the wood of the common yew (Fig. 17). 
If an exceedingly thin section of this wood be made, 
the very remarkable appearance will be shown which 
is exhibited in the illustration. The deposit has not 
only assumed the perfectly spiral form, but there 
are two complete spirals, arranged at some little 
distance from each other, and producing a very 
pretty effect when seen through a good lens. 

The pointed, elongated shape of the wood-cells 
is very well shown in the common elder-tree (see 
Fig. 15). In this instance the cells are without 
markings, but in general they are dotted like Fig. 21, 
an example cut from the woody part of the chrysan- 
themum stalk. This affords a very good instance of 
the wood-cell, as its length is considerable, and both 
ends are perfect in shape. On the right hand of 
the figure is a drawing of the wood-cell found in the 
lime-tree (Fig. 22), remarkable for the extremely 
delicate spiral markings with which it is adorned. 
In these wood-cells the secondary deposit is so 
plentiful that the original membranous character of 
the cell-walls is entirely lost, and they become elon- 



48 STOMA TA 

gated and nearly solid cases, having but a very small 
cavity in their centre. It is to this deposit that the 
hardness of wood is owing, and the reader will easily 
see the reason why the old wood is so much harder 
than the young and new shoots. In order to permit 
the passage of the fluids which maintain the life of 
the part, it is needful that the cell-wall be left thin 
and permeable in certain places, and this object is 
attained either by the " pits " described on page 43, 
or by the intervals between the spiral deposit. 

At the right-hand bottom corner of Plate I. (Fig. 
20) may be seen a prettily marked object, which is 
of some interest. It is a slice stripped from the 
outer coat of the holly-berry, and is given for the 
purpose of illustrating the method by which plants 
are enabled to breathe the atmospheric air on which 
they depend as much as ourselves, though their 
respiration is slower. Among the mass of net-like 
cells may be seen three curious objects, bearing a 
rather close resemblance to split kidneys. These 
are the mouths, or " stomata," as they are scientific- 
ally called. 

In the centre of the mouths may be seen a dark 
spot, which is the aperture through which the air 
communicates with the passages between the cells 
in the interior of the structure. In the flowering 
plants their shape is generally rounded, though they 
sometimes take a squared form, and they regularly 
occur at the meeting of several surface cells. The 
two kidney-shaped cells which form the " mouth " 
are the " guard-cells," so called from their function, 
since, by their change of form, they cause the mouth 



THEIR POSITION 4g 

to open or shut, according to the needs of the plant. 
In young plants these guard-cells are very little below 
the surface of the leaf or skin, but in others they 
are sunk quite beneath the layer of cells forming 
the outer coat of the tissue. There are other 
cases where they are slightly elevated above the 
surface. 

Stomata are found chiefly in the green portions 
of plants, and are most plentiful on the under side of 
leaves. It is, however, worthy of notice, that when 
an aquatic leaf floats on the water, the mouths are 
only to be found on the upper surface. These 
curious and interesting objects are to be seen in 
many structures where we should hardly think of 
looking for them ; for instance, they may be found 
existing on the delicate skin which envelops the 
kernel of the common walnut. As might be ex- 
pected, their dimensions vary with the character of 
the leaf on which they exist, being large upon the 
soft and pulpy leaves, and smaller upon those of a 
hard and leathery consistence. The reader will find 
ample amusement, and- will gain great practical 
knowledge of the subject, by taking a plant, say a 
tuft of groundsel, and stripping off portions of the 
external skin or " epidermis" from the leaf or stem, 
etc., so as to note the different sizes and shapes of 
the stomata. 

On the opposite bottom corner of Plate I. Fig. 25, 
is an example of a stoma taken from the outer skin 
of a gourd, and here given for the purpose of show- 
ing the curious manner in which the cells are 
arranged about the mouth, no less than seven cells 
4 



So SPECIAL EXAMPLES 

being placed round the single mouth, and the 
others arranged in a partially circular form around 
them. 

Turning to Plate II., we find several other ex- 
amples of stomata, the first of which (Fig. 1) is 
obtained from the under surface of the buttercup 
leaf, by stripping off the external skin, or " epider- 
mis," as it is scientifically termed. The reader will 
here notice the slightly waved outlines of the cell- 
walls, together with the abundant spots of chloro- 
phyll with which the leaf is coloured. In this 
example the stomata appear open. Their closure 
or expansion depends chiefly on the state of the 
weather ; and, as a general rule, they are open by 
day and closed at night. 

A remarkably pretty example of stomata and 
elongated cells is to be obtained from the leaf of the 
common iris, and may be prepared for the micro- 
scope by simply tearing off a strip of the epidermis 
from the under side of the leaf, laying it on a slide, 
putting a little water on it, and covering it with a 
piece of thin glass. (See Plate II. Fig. 2.) There 
are a number of longitudinal bands running along 
the leaf where these cells and stomata appear. 
The latter are not placed at regular intervals, for it 
often happens that the whole field of the microscope 
will be filled with cells without a single stoma, whilst 
elsewhere a group of three or four may be seen 
clustered closely together. 

Fig. 3 on the same Plate exhibits a specimen of 
the beautifully waved cells, without mouths, which 
are found on the upper surface of the ivy leaf. 



SPIRAL VESSELS 51 

These are difficult to arrange from the fresh leaf, 
but are easily shown by steeping the leaf in water 
for some time, and then tearing away the cuticle. 
The same process may be adopted with many leaves 
and cuticles, and in some cases the immersion must 
be continued for many days, and the process of 
decomposition aided by a very little nitric acid in 
the water, or by boiling. 

On the same Plate are three examples of spiral 
and ringed vessels, types of an endless variety of 
these beautiful and interesting structures. Fig. 4 
is a specimen of a spiral vessel taken from the lily, 
and is a beautiful example of a double spire. The 
deposit which forms this spiral is very strong, and 
it is to the vast number of these vessels that the 
stalk owes its well-known elasticity. In many cases 
the spiral vessels are sufficiently strong to be visible 
to the naked eye, and to bear uncoiling. For 
example, if a leaf-stalk of geranium be broken 
across, and the two fragments gently drawn asunder, 
a great number of threads, drawn from the spiral 
vessels, will be seen connecting the broken ends. 
In this case the delicate membranous walls of the 
vessel are torn apart, and the stronger fibre which 
is coiled spirally within it unrolls itself in propor- 
tion to the force employed. In many cases these 
fibres are so strong that they will sustain the weight 
of an inch or so of the stalk. 

In Fig. 5 is seen a still more bold and complex 
form of this curious structure ; being a coil of five 
threads, laid closely against each other, and forming, 
while remaining in their natural position, an almost 



52 ANALOGIES IN NATURE 

continuous tube. This specimen is taken from the 
root of the water lily, and requires some little care 
to exhibit its structure properly. 

Every student of nature must be greatly struck 
with the analogies between different portions of the 
visible creation. These spiral structures which we 
have just examined are almost identical in appear- 
ance, and to some extent in their function, with 
the threads that are coiled within the breathing 
tubes of insects. This is in both cases twofold, 
namely, to give support and elasticity to a delicate 
membrane, and to preserve the tube in its proper 
form, despite the bending to which it may be 
subjected. When we come to the anatomy of the 
insect in a future page we shall see this structure 
further exemplified. 

In some cases the deposit, instead of forming a 
spiral coil, is arranged in a series of rings, and tbe 
vessel is then termed " annulated." A very good 
example of this formation is given in Fig. 6, which 
is a sketch of such a vessel, taken from a stalk of 
the common rhubarb. To see these ringed vessels 
properly, the simplest plan is to boil the rhubarb 
until it is quite soft, then to break down the pulpy 
mass until it is flattened, to take some of the most 
promising portions with the forceps, lay them on 
the slide and press them down with a thin glass 
cover. They will not be found scattered at random 
through the fibres, which elsewhere present only 
a congeries of elongated cells, but are seen grouped 
together in bundles, and with a little trouble may 
be well isolated, and the pulpy mass worked away 




II. 



II AIRS 53 

so as to show them in their full beauty. As may 
be seen in the illustration, the number of the rings 
and their arrangement is extremely variable. A 
better, but somewhat more troublesome, plan is to 
cut longitudinal sections of the stem, as described 
in our concluding chapter, when not only the 
various forms of cells and vessels, but their 
relations to each other, will be well shown. The 
numerous crystals of oxalate of lime, which make 
rhubarb so injurious a food for certain persons, 
will also be well seen. These crystals are called 
" raphides," and are to be found in very many 
plants in different forms. 

The hairs of plants form very interesting 
objects, and are instructive to the student, as they 
afford valuable indications of the mode in which 
plants grow. They are all appendages of and arise 
from the skin or epidermis ; and although their 
simplest form is that of a projecting and elongated 
cell, the variety of shapes which are assumed by 
these organs is inexhaustible. On Plate IT. are 
examples of some of the more striking forms, 
which will be briefly described. 

The simple hair is well shown in Figs. 18, 19, 
and 32, the first being from the flower of the 
heartsease, the second from a dock-leaf, and the 
third from a cabbage. In Fig. 18 the hair is seen 
to be but a single projecting cell, consisting only of 
a wall and the contents. In Fig. 19 the hair has 
become more decided in shape, having assumed a 
somewhat dome-like form ; and in Fig. 3 2 it has 



54 FORKED AND BEADED HAIRS 

become considerably elongated, and may at once be 
recognised as a true hair. 

In Fig. 8 is a curious example of a hair taken 
from the white Arabis, one of the cruciferous 
flowers, which is remarkable for the manner in 
which it divides into two branches, each spreading 
in opposite directions. Another example of a 
forked hair is seen in Fig. 13, but in this instance 
the hair is composed of a chain of cells, the three 
lower forming the stem of the hair, and the two 
upper being lengthened into the lateral branches. 
This hair is taken from the common southernwood. 

In most cases of long hairs, the peculiar elon- 
gation is formed by a chain of cells, varying greatly 
in length and development. Several examples of 
these hairs will be seen on the same Plate. 

Fig. 9 is a beaded hair from the Marvel of Peru, 
which is composed of a number of separate cells 
placed end to end, and connected by slender threads 
in a manner that strongly reminds the observer of 
a chain of beads strung loosely together, so as to 
show the thread by which they are connected with 
each other. Another good example is seen at 
Fig. 11, in a hair taken from the leaf of the sow- 
thistle. In this case the beads are strung closely 
together, and when placed under a rather high 
power of the microscope have a beautifully white 
and pearly aspect. The leaf must be dry and quite 
fresh, and the hairs seen against the green of the 
leaf. Fig. 39 represents another beaded hair taken 
from the Virginian Spiderwort, or Tradescantia. 
This hair is found upon the stamens, and is 



LASHED HAIRS 55 

remarkable for the beautifully beaded outline, the 
fine colouring, and the spiral markings with which 
each cell is adorned. 

A still further modification of these many-celled 
hairs is found in several plants, where the hairs 
are formed by a row of ordinarily shaped cells, 
with the exception of the topmost cell, which is 
suddenly elongated into a whip-like form. Fig. 22 
represents a hair of this kind, taken from the 
common groundsel ; and Fig. 3 6 is a still more 
curious instance, found upon the leaf of the thistle. 
The reader may have noticed the peculiar white 
" fluffy " appearance of the thistle leaf when it is 
wet after a shower of rain. This appearance is 
produced by the long lash-like ends of the hairs, 
which are bent down by the weight of the moisture, 
and lie almost at right angles with the thicker 
portions of the hair. 

An interesting form of hair is seen in the 
" sting " of the common nettle. This may readily 
be examined by holding a leaf edgewise in the 
stage forceps, and laying it under the field of the 
microscope. In order to get the proper focus 
throughout the hair, the finger should be kept 
upon the screw movement, and the hair brought 
gradually into focus from its top to its base. The 
general structure of this hair is not unlike that 
which characterises the fang of a venomous serpent. 
The acrid fluid which causes the pain is situated in 
the enlarged base of the hair, and is forced through 
the long straight tubular extremity by means of 
the pressure exerted when the sting enters the 



56 STING OF NETTLE 

skin. At the very extremity of the perfect sting 
is a slight bulb-like swelling, which serves to 
confine the acrid juice, and which is broken 
off on the least pressure. The sting is seen in 
Fig. 43. 

The extremities of many hairs present very 
curious forms, some being long and slender, as in 
the examples already mentioned, while others are 
tipped with knobs, bulbs, clubs, or rosettes in 
endless variety. 

Fig. 12 is a hair of the tobacco leaf, exhibiting 
the two-celled gland at the tip, containing the 
peculiar principle of the plant, known by the name 
of " nicotine." The reader will see how easy it is 
to detect adulteration of tobacco by means of the 
microscope. The leaves most generally used for 
this purpose are the dock and the cabbage, so that 
if a very little portion of leaf be examined the 
character of the hairs will at once inform the 
observer whether he is looking at the real article 
or its substitute. 

Fig. 15 is a hair from the flower of the common 
yellow snapdragon, which is remarkable for the 
peculiar shape of the enlarged extremity, and for 
the spiral markings with which it is decorated. 
Fig. 16 is a curious little knobbed hair found 
upon the moneywort, and Fig. 17 is an example 
of a double-knobbed hair taken from the Geum. 
Fig. 34 affords a very curious instance of a 
glandular hair, the stem being built up of cells 
disposed in a very peculiar fashion, and the 
extremity being developed into a beautiful rosette- 



BRANCHED HAIRS 57 

shaped head. This hair came from the Garden 
Verbena. 

Curiously branched hairs are not at all un- 
common, and some very good and easily obtained 
examples are given on Plate II. 

Fig. 28 is one of the multitude of branched hairs 
that surround the well-known fruit of the plane- 
tree, the branches being formed by some of the 
cells pointing outward. These hairs do not assume 
precisely the same shape; for Fig. 29 exhibits 
another hair from the same locality, on which the 
spikes are differently arranged, and Fig. 30 is a 
sketch of another such hair, where the branches 
have become so numerous and so well developed 
that they are quite as conspicuous as the parent 
stem. 

One of the most curious and interesting forms 
of hair is that which is found upon the lavender 
leaf, and which gives it the peculiar bloom-like 
appearance on the surface. 

This hair is represented in Figs. 40 and 41. 
On Fig. 40 the hair is shown as it appears when 
looking directly * upon the leaf, and in Fig. 41 
a section of the leaf is given, showing the mode in 
which the hairs grow into an upright stem, and 
then throw out horizontal branches in every 
direction. Between the two upright hairs, and 
sheltered under their branches, may be seen a 
glandular appendage not unlike that which is 
shown in Fig. 1 6. This is the reservoir containing 
the perfume, and it is evidently placed under the 
spreading branches for the benefit of their shelter. 



58 OIL GLANDS 

On looking upon the leaf by reflected light the 
hairs are beautifully shown, extending their arms 
on all sides ; and the globular perfume cells may 
be seen scattered plentifully about, gleaming like 
pearls through the hair-branches under which they 
repose. They will be found more numerous on the 
under side of the leaf. 

This object will serve to answer a question which 
the reader has probably put to himself ere this, 
namely, Where are the fragrant resins, scents, and 
oils stored? On Plate I. Tig. 16, will be seen the 
reply to the first question ; Fig. 4 1 of the present 
Plate has answered the second question, and Pig. 
42 will answer the third. This figure represents a 
section of the rind of an orange, the flattened cells 
above constituting the delicate yellow skin, and the 
great spherical object in the centre being the re- 
servoir in which the fragrant essential oil is stored. 
The covering is so delicate that it is easily broken, 
so that even by handling an orange some of the 
scent is sure to come off on the hands, and when 
the peel is stripped off and bent double, the re- 
servoirs burst in myriads, and fling their contents 
to a wonderful distance. This may be easily seen 
by squeezing a piece of orange peel opposite a lighted 
candle, and noting the distance over which the oil 
will pass before reaching the flame, and bursting 
into little flashes of light. Other examples are 
given on the same plate. 

Eeturning to the barbed hairs, we may see in 
Fig. 35a highly magnified view of the " pappus " 
hair of a dandelion, i.e. the hairs which fringe the 



BARBED HAIRS- SPINES 59 

arms of the parachute-like appendage which is 
attached to the seed. The whole apparatus will 
be seen more fully on Plate III". Figs. 44, 45, 46. 
This hair is composed of a double layer of elongated 
cells lying closely against each other, and having 
the ends of each cell jutting out from the original 
line. A simpler form of a double-celled, or more 
properly a " duplex " hair, will be seen in Fig. 44. 
This is one of the hairs from the flower of the 
marigold and has none of the projecting ends to 
the cells. 

In some instances the cell-walls of the hairs 
become greatly hardened by secondary deposit, and 
the hairs are then known as spines. Two examples 
of these are seen in Figs. 37 and 38, the former 
being picked from the Indian fig-cactus, and well 
known to those persons who have been foolish 
enough to handle the fig roughly before feeling it. 
The wounds which these spines 'will inflict are said 
to be very painful, and have been compared to 
those produced by the sting of the wasp. The 
latter hair is taken from the Opuntia. These spines 
must not be confounded with thorns ; which latter 
are modified branches. 

Fig. 1 represents the extreme tip of a hair from 
the hollyhock leaf, subjected to a lens of very high 
power. 

Many hairs assume a star-like appearance, an 
aspect which may be produced in different ways. 
Sometimes a number of simple hairs start from the 
same base, and by radiating in different directions 
produce the stellate effect. An example of this 



60 KNOBBED HAIRS 

kind of hair may be seen in Fig. 14, which is a 
group of hairs from the hollyhock leaf. There is 
another mode of producing the star-shape which 
may be seen in Fig. 45, a hair taken from the leaf 
of the ivy. Very fine examples may also be found 
upon the leaf of Deutzia scabra. 

Hairs are often covered with curious little 
branches or protuberances, and present many other 
peculiarities of form which throw a considerable 
light upon certain problems in scientific microscopy. 

Fig. 33 represents a hair of two cells taken 
from the flower of the well-known dead-nettle, 
which is remarkable for the number of knobs 
scattered over its surface. A similar mode of 
marking is seen in Fig. 31, a club-shaped hair 
covered with external projections, found in the 
flower of the Lobelia. In order to exhibit these 
markings well, a power of two hundred diameters 
is needed. Fig. 21 shows this dotting in another 
hair from the dead-nettle, where the cell is drawn 
out to a great length, but is still covered with these 
markings. 

Fig. 20 is an example of a very curious hair 
taken from the throat of the pansy. This hair 
may readily be obtained by pulling out one of the 
petals, when the hairs will be seen at its base. 
Under the microscope it has a particularly beautiful 
appearance, looking just like a glass walking-stick 
covered with knobs, not unlike those huge, knobby 
club -like sticks in which some farmers delight, 
where the projections have been formed by the 
pressure of a honeysuckle or other climbing plant. 



BARK CELLS 61 

A hair of a similar character, but even more 
curious, is found in the same part of the flower of 
the Garden Verbena (see Fig. 27), and is not only 
beautifully translucent, but is coloured according to 
the tint of the flower from which it is taken. Its 
whole length is covered with large projections, the 
joints much resembling the antennas of certain 
insects ; and each projection is profusely spotted 
with little dots, formed by elevation of the outer 
skin or cuticle. These are of some value in deter- 
mining the structure of certain appearances upon 
petals and other portions of the flowers, and may be 
compared with Figs. 33 to 35 on Plate III. 

Fig. 26 offers an example of the square cells 
which usually form the bark of trees. This is a 
transverse section of cork, and perfectly exhibits 
the form of bark cells. The reader is very strongly 
advised to cut a delicate section of the bark of 
various trees, a matter very easily accomplished 
with the aid of a sharp razor and a steady hand. 

Fig 24 is a transverse section through one of the 
scales of a pine-cone, and is here given for the 
purpose of showing the numerous resin-filled cells 
which it displays. This may be compared with 
Fig. 16 of Plate I. Fig. 25 is a part of one of 
the " vittfe," or oil reservoirs, from the fruit of the 
caraway, showing the cells containing the globules 
of caraway oil. This is rather a curious object, 
because the specimen from which it was taken was 
boiled in nitric acid, and yet retained some of the 
oil globules. Immediately above it may be seen 
(Fig. 23) a transverse section of the beechnut, 



62 FLINT IN PLANTS 

showing a cell with its layers of secondary 
deposit. 

In the cuticle of the grasses and the mare's- 
tails is deposited a large amount of pure flint. So 
plentiful is this substance, and so equally is it 
distributed, that it can be separated by heat or 
acids from the vegetable parts of the plant, and 
will still preserve the form of the original cuticle, 
with its cell-walls, stomata, and hairs perfectly well 
denned. 

Fig. 7, Plate II., represents a piece of wheat 
chaff, or " bran," that has been kept at a white heat 
for some time, and then mounted in Canada balsam. 
I prepared the specimen from which the drawing 
was made by laying the chaff on a piece of 
platinum, and holding it over the spirit-lamp. A 
good example of the silex or flint in wheat is often 
given by the remains of a straw fire, where the 
stems may be seen still retaining their tubular form 
but fused together into a hard glassy mass. It is 
this substance that cuts the fingers of those who 
handle the wild grasses too roughly, the edges of 
the blades being serrated with flinty teeth, just like 
the obsidian swords of the ancient Mexicans, or the 
shark's-tooth falchion of the New Zealander. 

These are but short and meagre accounts of a 
very few objects, but space will not permit of 
further elucidation, and the purpose of this little 
work is not to exhaust the subjects of which it 
treats, but to incite the reader to undertake in- 
vestigation on his own account, and to make his 
task easier than if he had done it unaided. 



STARCH 63 



CHAPTER V 

Starch, its Growth and Properties — Surface Cells of Petals 
— Pollen and its Functions — Seeds. 

The white substance so dear to the laundries under 
the name of starch is found in a vast variety of 
plants, being distributed more widely than most of 
the products which are found in the interior of 
vegetable cells. 

The starch grains are of very variable size even 
in the same plant, and their form is as variable as 
their size, though there is a general resemblance in 
those of the same plant which allows of their being 
fairly easily identified after a moderate amount of 
practice. Sometimes the grains are found loosely 
packed in the interior of the cells, and are then 
easily recognised as starch grains by their peculiar 
form and the delicate lines with which they are 
marked ; but in many places they are pressed so 
closely together that they assume an hexagonal 
shape under the microscope, and bear a close resem- 
blance to ordinary twelve-sided cells. In other 
plants, again, the grains never advance beyond (he 
very minute form in which they seem to commence 
their existence ; and in some, such as the common 
oat, a great number of very little granules are 



64 IODINE AND STARCH • 

compacted together so as to resemble one large 
grain. 

There are several methods of detecting starch in 
those cases where its presence is doubtful ; and the 
two modes that are usually employed are polarised 
light and the iodide of potassium. When polarised 
light is employed — a subject on which we shall 
have something to say presently — the starch grains 
assume the characteristic " black-cross," and when 
a plate of selenite is placed immediately beneath 
the slide containing the starch grains, they glow 
with all the colours of the rainbow. The second 
plan is to treat them with a very weak solution of 
iodine and iodide of potassium, and in this case the 
iodine has the effect on the starch granules of 
staining them blue. They are so susceptible of 
this reaction that when the liquid is too strong the 
grains actually become black from the amount of 
iodine which they imbibe. 

Nothing is easier than to procure starch granules 
in the highest perfection. Take a raw potato, and 
with a razor cut a very thin slice from its interior, 
the direction of the cut not being of the slightest 
importance. Put this delicate slice upon a slide, 
drop a little water upon it, cover it with a piece of 
thin glass, give id a guod squeeze, and place it 
under a power of a hundred or a hundred and fifty 
diameters. Any part of the slice, provided that it 
be very thin, will then present the appearance 
shown in Plate III. Pig. 9, where an ordinary cell 
of potato is seen filled loosely with starch grains 
of different sizes. Around the edges of the slice a 




WM1 






39 K, , 3 




35 



TO/ 

,1 C/^, 




in. 



STARCH FROM POTATO 65 

vast number of starch granules will be seen, which 
have been squeezed out of their cells by pressure, 
and are now floating freely in the water. As cold 
water has no perceptible effect upon starch, the 
grains are not altered in form by the moisture, and 
can be examined at leisure. 

On focusing with great care, the surface of each 
granule will be seen to be covered with very minute 
dark lines, arranged in a manner which can be 
readily comprehended from Fig. 4, which represents 
two granules of potato starch as they appear when 
removed from the cell in which they took their 
origin. All the lines evidently refer to the little 
dark spots at the end of the granule, called 
technically the " hilum," and represent the limits of 
successive layers of material deposited one after 
another. The lines in question are very much 
better seen if the substage condenser be used with 
a small central stop, so as to obtain partial dark- 
field illumination. Otherwise they are often very 
difficult of detection. 

In the earliest stages of their growth the starch 
granules appear to be destitute of these markings, 
or at all events they are so few and so delicate as 
not to be visible even with the most perfect in- 
struments, and it is not until the granules assume 
a comparatively large size that the external mark- 
ings become distinctly perceptible. 

We will now glance at the examples of starch 
which are given in the Plate, and which are a very 
few out of the many that might be figured. Fig. 2 
represents the starch of wheat, the upper grain 



66 WHEAT AND ARROWROOT 

being seen in front, the one immediately below it 
in profile, and the two others being examples of 
smaller grains. Fig. 6 is a specimen of a very- 
minute form of starch, where the granules do not 
seem to advance beyond their earliest stage. This 
specimen is obtained from the parsnip ; and al- 
though the magnifying power is very great, the 
dimensions of the granules are exceedingly small, 
and except by a very practised eye they would not 
be recognisable as starch grains. 

Fig. 3 is a good example of a starch grain of 
wheat, exemplifying the change that takes place 
by the combined effects of heat and moisture. It 
has already been observed that cold water exercises 
little, if any, perceptible influence upon starch ; but 
it will be seen from the illustration that hot water 
has a very powerful effect. When subjected to the 
action of water at a temperature over 140° Fahr., 
the granule swells rapidly, and at last bursts, the 
contents escaping in a gelatinous mass, and the 
external membrane collapsing into the form which 
is shown in Fig. 3, which was taken out of a piece 
of hot pudding. A similar form of wheat starch 
may also be detected in bread, accompanied, un- 
fortunately, by several other substances not generally 
presumed to be component parts of the " staff of life." 

In Fig. 7 are represented some grains of starch 
from West Indian arrowroot, and Fig. 8 exhibits 
the largest kind of starch grain known, obtained 
from the tuber of a species of canna, supposed to 
be C. edtilis, a plant similar in characteristics to 
the arrowroot. The popular name of this starch is 



MAIZE AND TAPIOCA 67 

" Tous les Mois," and under that title it may be 
obtained from the opticians, or chemists. 

Fig. 10 shows the starch granules from Indian 
corn, as they appear before they are compressed 
into the honeycomb - like structure which has 
already been mentioned. Even in that state, 
however, if they are treated with iodine, they 
exhibit the characteristics of starch in a very 
perfect manner. Fig. 11 is starch from sago, and 
Fig. 12 from tapioca, and in both these instances 
the several grains have been injured by the heat 
employed in preparing the respective substances 
for the market. 

Fig. 13 exhibits the granules obtained from the 
root of the water-lily, and Fig. 14 is a good 
example of the manner in which the starch granules 
of rice are pressed together so as to alter the 
shape and puzzle a novice. Fig. 16 is the com- 
pound granule of the oat, which has already been 
mentioned, together with some of the simple 
granules separated from the mass ; and Fig. 1 5 
is an example of the starch grains obtained from 
the underground stem of the horse-bean. It is 
worthy of mention that the close adhesion of the 
rice starch into those masses is the cause of the 
peculiar grittiness which distinguishes rice flour to 
the touch. 

Whilst very easily acted on by heat, starch- 
granules are very resistent to certain other 
reagents. Weak alkalies, in watery solution, 
readily attack them, but by treating portions of 
plants with caustic potash dissolved in strong 



68 EPIDERMIS OF PLANTS 

spirit, the woody and other parts may be dissolved 
away ; and after repeated washing with spirit the 
starch may be mounted. This, however, must 
never be in any glycerine medium, except that 
given on p. 172. 

In Plate III. Fig. 1, may be seen a curious little 
drawing, which is a sketch of the laurel-leaf cut 
transversely, aud showing the entire thickness of 
the leaf. Along the top may be seen the delicate 
layer of " varnish " with which the surface of the 
leaf is covered, and which serves to give to the 
foliage its peculiar polish. This varnish is nothing 
more than the translucent matter which binds all 
the cells together, and which is poured out very 
liberally upon the surface of the leaf. The lower 
part of this section exhibits the cells of which the 
leaf is built, and towards the left hand may be seen 
a cut end of one of the veins of the leaf, more 
rigidly called a wood-cell. 

"We will now examine a few examples of surface 
cells. 

Fig. 5 is a portion of epidermis stripped from a 
Capsicum pod, exhibiting the remains of the nuclei 
in the centre of each cell, together with the great 
thickening of the wall-cells and the numerous pores 
for the transmission of fluid. This is a very pretty 
•specimen for the microscope, as it retains its bright 
red colour, and even in old and dried pods exhibits 
the characteristic markings. 

In the centre of the Plate may be seen a wheel- 
like arrangement of the peculiar cells found on the 



PETALS 69 

petals of six different flowers, ail easily obtainable, 
and mounted witliout difficulty. 

Fig. 30 is the petal of a geranium (Pelargonium), 
a very common object on purchased slides. It is 
a most lovely subject for the microscope, whether 
it be examined with a low or a high power, — in 
the former instance exhibiting a most beautiful 
" stippling " of pink, white, and black, and in the 
latter showing the six-sided cells with their curious 
markings. 

In the centre of each cell is seen a radiating 
arrangement of dark lines with a light spot in the 
middle, looking very like the mountains on a map. 
These lines were long thought to be hairs ; but 
Mr. Tuffen West, in an interesting and elaborate 
paper on the subject, has shown their true nature. 
From his observations it seems that the beautiful 
velvety aspect of flower petals is owing to these 
arrangements of the surface cells, and that their 
rich brilliancy of colour is due to the same cause. 
The centre of each cell- wall is elevated as if pushed 
up by a pointed instrument from the under side of 
the wall, and in different flowers this elevation 
assumes different forms. Sometimes it is merely 
a slight wart on the surface, sometimes it becomes 
a dome, while in other instances it is so developed 
as to resemble a hair. Indeed, Mr. West has con- 
cluded that these elevations are nothing more than 
rudimentary hairs. 

The dark radiating lines are shown by the same 
authority to be formed by wrinkling of the 
membrane forming the walls of the eleyated 



70 PETALS 

centre, and not to be composed of "secondary 
deposit," as has generally been supposed. 

Fig. 31 represents the petal of the common 
periwinkle, differing from that of the geranium by 
the straight sides of the cell-walls, which do not 
present the toothed appearance so conspicuous in 
the former flower. A number of little tooth -like 
projections may be seen on the interior of the cells, 
their bases affixed to the walls and their points 
tending toward the centre, and these teeth are, 
according to Mr. "West, formed of secondary 
deposit. 

In Fig. 32 is shown the petal of the common 
garden balsam, where the cells are elegantly 
waved on their outlines, and have plain walls. 
The petal of the primrose is seen in Fig. 34, and 
that of the yellow snapdragon in Fig. 33; in the 
latter instance the surface cells assume a most 
remarkable shape, running out into a variety of 
zigzag outlines that quite bewilders the eye when 
the ohjeel is first placed under the microscope. 
Fig. 35 is the petal of the common scarlet 
geranium. 

In several instances these petals are too thick 
to be examined without some preparation, and 
glycerine will be found well adapted for that 
purpose. The young microscopist must, however, 
beware of forming his ideas from preparations of 
dried leaves, petals, or hairs, and should always 
procure them in their fresh state whenever he 
desires to make out their structure. Even a fading 
petal should not be used, and if the flowers are 



POLLEN 71 

gathered for the occasion, thoir .stalks should be 
placed in water, so as to give a series of leaves and 
petals as fresh as possible. 

We now pass from the petal of the flower to the 
pollen, that coloured dust, generally yellow or 
white, which is found upon the stamens, and which 
is very plentiful in many flowers, such as the lily 
and the hollyhock. 

This substance is found only upon the stamens 
or anthers of full-blown flowers (the anthers being 
the male organs), and is intended for the purpose 
of enabling the female portion of the flower to 
produce fertile seeds. In form the pollen grains 
are wonderfully diverse, affording an endless variety 
of beautiful shapes. In some cases the exterior is 
smooth and marked only with minute dots, but in 
many instances the outer wall of the pollen grain 
is covered with spikes, or decorated with stripes or 
belts. A few examples of the commonest forms of 
pollen will be found on Plate III. 

Fig. 17 is the pollen of the snowdrop, which, as 
will be seen, is covered with dots and marked with 
a definite slit along its length. The dots are 
simply tubercles in the outer coat of the grain, and 
are presumed to be formed for the purpose of 
strengthening the membrane, otherwise too delicate, 
upon the same principle which gives to "corrugated " 
iron such strength in proportion to the amount of 
material. Fig. 18 is the pollen of the wall-flower, 
shown in two views, and having many of the same 
characteristics as that of the snowdrop. Fig. 19 



72 ACTION OF POLLEN 

is the pollen of the willow-herb, and is here given 
as an illustration of the manner in which the 
pollen aids in the germination of plants. 

In order to understand its action, we must first 
examine its structure. 

All pollen-grains are furnished with some means 
by which their contents when thoroughly ripened 
can be expelled. In some cases this end is accom- 
plished by sundry little holes called pores ; in 
others, certain tiny lids are pushed up by the 
contained matter ; and in some, as in the present 
instance, the walls are thinned in certain places so 
as to yield to the internal pressure. 

When a ripe pollen -grain falls upon the stigma 
of a flower, it immediately begins to swell, and 
seems to " sprout " like a potato in a damp cellar, 
sending out a slender " pollen-tube " from one or 
other of the apertures already mentioned. In 
Fig. 19 a pollen-tube is seen issuing from one 
of the projections, and illustrates the process better 
than can be achieved by mere verbal description. 
The pollen-tubes insinuate themselves between the 
cells of the stigmas, and, continually elongating, 
worm their way down the " style " until fifcey come 
in contact with the " ovules." By very careful 
dissection of a fertilised- stigma, the beautiful sight 
of the pollen-tubes winding along the tissues of the 
style may be observed under a high power of the 
microscope. 

The pollen-tube is nothing more than the interior 
coat of the grain, very much developed, and filled 
with a" substance technically named " fovilla," com- 



MARKINGS ON POLLEN 73 

pcw.il of " protoplasm " (tlie semi-liquid substance 
whicli is found in the interior of cells), very minute 
starch grains, and some apparently oily globules. 

In order to examine the structure of the pollen- 
grains properly, they should be examined under 
various circumstances — some dry, others placed in 
water to which a little sugar has been added, others 
in oil, and it will often be found useful to try the 
effect of different acids upon them. 

Fig. 20 is the pollen of the common violet, and 
is easily recognisable by its peculiar shape and 
markings. Fig. 21 is the pollen of the musk-plant, 
and is notable for the curious mode in which its 
surface is belted with wide and deep bands, run- 
ning spirally round the circumference. Fig. 22 
exhibits the pollen of the apple, and Fig. 23 
affords a very curious example of the raised 
markings upon the surface of the dandelion pollen. 
In Fig. 24 there are also some very wonderful 
markings, but they are disposed after a different 
fashion, forming a sort of network upon the sur- 
face, and leaving several large free spaces between 
the meshes. The pollen of the lily is shown in 
Fig. 25, and is a good example of a pollen-grain 
covered with the minute dottings which have 
already been described. 

Figs. 2 6 and 2 7 show two varieties of compound 
pollen, found in two species of heath. These 
compound pollen-grains are not of unfrequent occur- 
rence, and are accounted for in the following manner. 

The pollen is formed in certain cavities within the 
anthers, by means of the continual subdivision of 



74 FORMA TION OF POLLEN 

the " parent-cells " from which it is developed. In 
many cases the form of the grain is clearly owing 
to the direction in which these cells have divided, 
but there is no great certainty on this subject. 
It will be seen, therefore, that if the process of 
subdivision be suddenly arrested, the grains will 
be found adhering to each other in groups of 
greater or smaller size, according to the character 
of the species and the amount of subdivision that 
has taken place. The reader must, however, bear 
in mind that the whole subject is as yet rather 
obscure, and that further discovery may throw 
doubt on many theories which at present are 
accepted as established. 

Fig. 28 shows the pollen of the furze, in which 
are seen the longitudinal slits and the numerous dots 
on the surface; and Fig. 29 is the curiously shaped 
pollen of the tulip. The two large yellow globular 
figures at each side of the Plate represent the pollen 
of two common flowers ; Fig. 3 6 being that of the 
crocus, and Fig. 37 a pollen-grain of the hollyhock. 
As may be seen from the illustration, the latter 
is of considerable size, and is covered with very 
numerous projections. These serve to raise the 
grain from a level surface, over which it rolls 
with a surprising ease of motion, so much so in- 
deed that if a little of this substance be placed on 
a slide and a piece of thin glass laid over it, the 
glass slips off as soon as it is in the least inclined, 
and forces the observer to fix it with paper or 
cement before he can place it on the inclined 
stage of the microscope. The little projections 



SFFDS 75 

have a very curious effect under a liij^li ]>uwer, 
and require careful focusing to observe them 
properly ; for the diameter of the grain is so largo 
that the focus must be altered to suit each indi- 
vidual projection. Their office is. probably, to aid 
in fertilisation. 

The seeds of plants are even easier of examina- 
tion than the pollen, and in most cases require 
nothing but a pocket lens and a needle for making 
out their general structure. The smaller seeds, 
however, must be placed under the microscope, 
many of them exhibiting very curious forms. The 
external coat of seeds is often of great interest, 
and needs to be dissected off before it can be 
rightly examined. The simplest plan in such a 
case is to boil the seed well, press it- while still 
warm into a plate of wax, and then dissect with a 
pair of needles, forceps, and scissors under water. 
Many seeds may also be mounted in cells as dry 
objects, after being thoroughly dried themselves. 

A few examples of the seeds of common plants 
are given at the bottom of Plate III. 

Fig. 38 exhibits the fruit, popularly called the 
seed, of the common goosegrass, or Galium, which 
is remarkable for the array of hooklets with which 
it is covered. Immediately above the figure may 
be seen a drawing of one of the hooks much 
magnified, showing its sharp curve (Fig. 39). It 
is worthy of remark that the hook is not a simple 
curved hair, but a structure composed of a number 
of cells terminating in a hook. 



76 PLUMED SEEDS 

Fig. 40 shows the seed, or rather the fruit, of 
the common red valerian, and is introduced for the 
purpose of showing its plumed extremity, which 
acts as a parachute, and causes it to be carried 
about by the wind until it meets with a proper 
resting-place. It is also notable for the series of 
strong longitudinal ribs which support its external 
structure. On Fig. 41 is shown a portion of one 
of the parachute hairs much more magnified. 

The seed of the common dandelion, so dear to 
children in their play-hours, when they amuse 
themselves by puffing at the white plumy globes 
which tip the ripe dandelion flower-stalks, is a very 
interesting object even to their parents, on account 
of its beautiful structure, and the wonderful way 
in which it is adapted to the place which it fills. 
Fig. 45 represents the seed portion of one of these 
objects, together with a part of the parachute 
stem, the remainder of that appendage being shown 
lying across the broken stem. 

The shape of the seed is not unlike that of the 
valerian, but it is easily distinguished from that 
object by the series of sharp spikes which fringe 
its upper end, and which serve to anchor the seed 
firmly as soon as it touches the ground. From 
this end of the seed proceeds a long slender shaft, 
crowned at its summit by a radiating plume of 
delicate hairs, each of which is plentifully jagged 
on its surface, as may be seen in Fig. 46, which 
shows a small portion of one of these hairs greatly 
magnified. These jagged points are evidently in- 
tended to serve the same purpose as the spikes 



BARBED SEEDS 77 

below, and to arrest the progress of the seed as 
soon as it has found a convenient spot. 

Kg. 42 is the seed of the foxglove, and Fig. 43 
the seed of the sunspurge, or milkwort. Fig. 47 
shows the seed of the yellow snapdragon ; remark- 
able for the membranous wing with which the seed 
is surrounded, and which is composed of cells with 
partially spiral markings. When viewed edgewise, 
it looks something like Saturn with his ring, or, to 
use a more homely but perhaps a more intelligible 
simile, like a marble set in the middle of a penny. 
Fig. 48 is a seed of mullein, covered with net-like 
markings on its external surface. These are prob- 
ably to increase the strength of the external coat, 
and are generally found in the more minute seeds. 

On Fig. 5 is shown a seed of the burr-reed ; a 
structure which is remarkable for the extraordinary 
projection of the four outer ribs, and their powerful 
armature of reverted barbs. Fig. 51 shows another 
form of parachute seed, found in the willow-herb, 
where the parachute is not expanded nearly so 
widely as that of the valerian ; neither is it set 
upon a long slender stem like that of the dandelion, 
but proceeds at once from the top of the seed, 
widening towards the extremity, and having a very 
comet-like appearance. Two more seeds only re- 
main, Fig. 49 being the seed of Eobin Hood, and 
the other, Fig. 52, that of the muskmallow, being 
given in consequence of the thick coat of hairs with 
which it is covered. 

Many seeds can be well examined when mounted 
in Canada balsam. 



78 THE LOWEST VEGETABLE FORMS 



CHAPTER VI 

Algse and their Growth — Desmidiacese, where found — 
Diatoms, their Flinty Deposit — Volvox — Mould, Blight, 
and Mildew — Mosses and Ferns — Mare's-Tail and the 
Spores — Common Sea-weeds and their Growth. 

On Plate IV will be seen many examples of the 
curious vegetables called respectively algse and 
fungi, which exhibit some of the lowest forms of 
vegetable life, and are remarkable for their almost 
universal presence in all parts of this globe, and 
also almost all conditions of cold, heat, or climate. 
Many of them are well known under the popular 
name of sea-weeds, others are equally familiar 
under the titles of " mould," " blight," or " mildew," 
while many of the minuter kinds exhibit such 
capability of motion, and such apparent symptoms 
of volition, that they have long been described as 
microscopic animalcules, and thought to belong to 
the animal rather than to the vegetable kingdoms. 

Fig. 1 represents one of the very lowest forms 
of vegetable life, being known to the man of science 
as the Palmella, and to the general public as 
'gory dew." It may be seen on almost any damp 
wall, extending in red patches of various sizes, 
looking just as if some blood had been dashed on 



ALGM 79 

the wall, and allowed to dry there. With a 
tolerably powerful lens this substance can be 
resolved into the exceedingly minute cells depicted 
in the figure. Generally, these cells are single, but 
in many instances they are double, owing to the 
process of subdivision by which the plant grows, if 
such a term may be used. 

Fig. 2 affords an example of another very low 
form of vegetable, the Palmoglaea, that green slimy 
substance which is so common on damp stones. 
When placed under the microscope, this plant is 
resolvable into a multitude of green cells, each 
being surrounded with a kind of gelatinous sub- 
stance. The mode of growth of this plant is very 
simple. A line appears across one of the cells, and 
after a while it assumes a kind of hour-glass aspect, 
as if a string had been tied tightly round its middle. 
By degrees the cell fairly divides into two parts, 
and then each part becomes surrounded with its 
own layer -of gelatine, so as to form two separate 
cells, placed end to end. 

One of the figures, that on the right hand, 
represents the various processes of " conjugation," 
i.e. the union and fusion together of two cells. 
Each cell throws out a little projection ; these meet 
together, and then uniting, form a sort of isthmus 
connecting the two main bodies. This rapidly 
widens, until the two cells become fused into one 
large body. The whole subject of conjugation is 
very interesting, and is treated at great length in the 
Micrographic Dictionary of Messrs. Griffith and 
Henfrey, a work to which the reader is referred 



80 MUL TI PLICA TION BY DI VISION 

for further information on many of the subjects 
that, in this small work, can receive but a very 
hasty treatment. 

Few persons would suppose that the slug-like 
object on Fig. 3, the little rounded globules with a 
pair of hair-like appendages, and the round disc 
with a dark centre, are only different forms of the 
same organism. Such, however, is the case, and 
these are three of the modifications which the 
Protococcus undergoes. This vegetable may be 
seen floating like green froth on the surface of 
rain-water. 

On collecting some of this froth and putting it 
under the microscope, it is seen to consist of a vast 
number of little green bodies, moving briskly about 
in all directions, and guiding their course with such 
apparent exercise of volition that they might very 
readily be taken for animals. It may be noticed 
that the colour of the plant is sometimes red, and 
in that state it has been called the Hcematococcus. 

The " still " state of this plant is shown in the 
round disc. After a while the interior substance 
splits into two portions ; these again subdivide, and 
the process is repeated until sixteen or thirty-two 
cells become developed out of the single parent-cell. 
These little ones then escape, and, being furnished 
with two long " cilia " or thread-like appendages, 
whirl themselves merrily through the water. 
When they have spent some time in this state, 
growing all the while, they lose their cilia, become 
clothed with a strong envelope, and pass into the 
still stage from which they had previously emerged. 



'mm > A 





<J> ^ 27 , _ 28 \ ~^--- a 



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> so ot SSt 88 SI jo j J I 

r ' JSf jptfjtf jtf jtf S3 2g jg 

B8af83S888 39S8 3, 

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IV. 



THE DESMIDS 81 

This curious process is repeated in endless succession, 
and causes a very rapid growth of the plant. The 
moving bodies are technically called zoospores, or 
living spores, and are found in many other plants 
besides those of the lowest order. 

On Fig. 13 is delineated a very minute plant, 
called from its colour Chlorococcus. It may be 
found upon tree-trunks, walls, etc., in the form of 
green dust, and has recently been found to take 
part in forming the first stage of lichens. 

A large and interesting family of the " confer- 
void algas," as these low forms of vegetable life are 
termed, is the Desmidiaceag, called in more common 
parlance desmids. A few examples of this family 
are given in Plate IV. 

They may be found in water, always preferring 
the cleanest and the brightest pools, mostly con- 
gregating in masses of green film at the bottom of 
the water, or investing the stems of plants. Their 
removal is not very easy, but is best accomplished 
by very carefully taking up this green slippery 
substance in a spoon, and straining the water away 
through fine muslin. They may also be separated 
by allowing a ring, covered with muslin, to float 
upon the surface of the water collected in a jar, 
for, being great lovers of light, they assemble where 
it is most abundant. An opaque jar should be 
used. For preservation, glycerine-gelatine seems 
to be the best fluid. A very full and accurate 
description of these plants may be found in Ealfs' 
British Desrnidiece. 

Fig. 4 represents one of the species of Closterium, 
6 



82 REPRODUCTION OF DESMIDS 

more than twenty of which are known. These 
beautiful objects can be obtained from the bottom 
of almost every clear pool, and are of some interest 
on account of the circulating currents that may be 
seen within the living plants. A high power is 
required to see this phenomenon clearly. The 
Closteria are reproduced in various ways. Mostly 
they divide across the centre, being joined for a 
while by two half-cells. Sometimes they repro- 
duce by means of conjugation, the process being 
almost entirely conducted on the convex sides. 
Fig. 5 represents the end of a Closterium, much 
magnified in order to show the actively moving 
bodies contained within it. 

Fig. 16 is a supposed desmid, called Ankistro- 
desmus, and presumed to be an earlier stage of 
Closterium. 

Fig. 6 is a very pretty desmid called the 
Pediastrum, and valuable to the microscopist as 
exhibiting a curious mode of reproduction. The 
figure shows a perfect plant composed of a number 
of cells arranged systematically in a star-like shape ; 
Fig. 15 is the same species without the colouring 
matter, in order to show the shape of the cells. 
The Pediastrum reproduces by continual subdivision 
of the contents of each cell into a number of 
smaller cells, termed " gonidia " on account of their 
function on the perpetuation of the species. When 
a sufficient number has been formed, they burst 
through the envelope of the original cell, taking 
with them a portion of its internal layer, so as to 
form a vesicle, in which they move actively. Tn a 



VARIETIES OF FORM 83 

few minutes they arrange themselves in a circle, 
and after a while they gradually assume the perfect 
form, the whole process occupying about two days. 
Fig. 18 exhibits an example of the genus Des- 
midium. In tins genus the cells are either square 
or triangular in their form, having two teeth at 
their angles, and twisted regularly throughout their 
length, causing the wavy or oblique lines which 
distinguish them. The plants of this genus are 
common, and may be found almost in any water. 
I may as well mention that I have obtained nearly 
all the preceding species, together with many others, 
from a little pond on Blackhsath. 

Fig. 7 is another desmid called Scenedesmus, in 
which the cells are arranged in rows of from two 
to ten in number, the cell at each extremity being 
often furnished with a pair of bristle-like append- 
ages. Fig. 14 is another species of the same 
plant, and both may be found in the water supplied 
for drinking in London, as well as in any pond. 

A common species of desmid is seen at Fig. 12, 
called Sphserozosma, looking much like a row of 
stomata set chainwise together. It multiplies by 
self-division. 

Fig. 17 is a specimen of desmid named Cosmar- 
ium, plentifully found in ponds on heaths and 
commons, and having a very pretty appearance 
in the microscope, with its glittering green centre 
and beautifully transparent envelope. The manner 
in which the Cosmarium conjugates is very re- 
markable, and is shown at Fig. 19. 

The two conjugating cells become very deeply 



84 OSCILLATORIA 

cleft, and by degrees separate, suffering the contents 
to pour out freely, and, as at present appears, with- 
out any envelope to protect them. The mass, 
however, soon acquires an envelope of its own, and 
by degrees assumes a dark reddish-brown tint. It 
is now termed a sporangium, and is covered with a 
vast number of projections, which in this genus 
are forked at their tip, but in others, which also 
form sporangia, are simply pointed. The Closteria 
conjugate after a somewhat similar manner, and it 
is not unfrequent to find a pair in this condition, 
but in their case the sporangium is quite smooth 
on its surface. 

Another very remarkable family of confervoid 
algae is that which is known under the name of 
Oscillatorise, from the oscillating movement of the 
plant. They are always long and filamentous in 
character, and may be seen moving up and down 
with a curious irregularity of motion. Their 
growth is extremely rapid, and may be watched 
under a tolerably powerful lens, thus giving many 
valuable hints as to the mode by which these 
plants are reproduced. One of the commonest 
species is represented at Fig. 8. 

Figs. 9, 10, afud 11 are examples of another 
family, called technically the Zygnemacese, because 
they are so constantly yoked together by conjuga- 
tion. They all consist of a series of cylindrical 
cells, set end to end, and having their green 
contents arranged in similar patterns. Two of the 
most common and typical species are here given. 

Fig. 9 is the Spirogyra, so called from the 



D1AT0MACRM 85 

spiral arrangement of the chlorophyll ; and Fig. 10 
is the Tyndaridea, or Zygnoma, as it is called by 
some writers. A casual inspection will show how 
easy it is to distinguish the one from the other. 
Fig. 11 represents a portion of the Tyndaridea 
during the process of conjugation, showing the tube 
of connection between the cells and one of the 
spores. 

We now arrive at the diatoms, so called because 
of their method of reproduction, in which it appears 
as if a cut were made right along the original cell. 
The commonest of these plants is the Diatoma 
vulgare, seen in Fig. 21 as it appears while growing. 
The reproduction of this plant is effected by split- 
ting down the centre, each half increasing to the 
full size of the original cell; and in almost every 
specimen of water taken from a pond, examples of 
this diatom undergoing the process of division will 
be distinguished. It also grows by conjugation. 
The diatoms are remarkable for the delicate shell 
or flinty matter which forms the cell skeleton, and 
which will retain its shape even after intense heat 
and the action of nitric acid. While the diatoms 
are alive, swimming through the water, their 
beautiful markings are clearly distinct, glittering 
as if the form were spun from crystalline glass. 
Just above the figure, and to the right hand, are 
two outlines of single cells of this diatom, the 
one showing the front veiw and the other the 
profile, 

Fig. 20 is an example of a diatom — Cocconema 



86 FRESH WATER FORMS 

lanceolatum — furnished with a stalk. The left- 
hand branch sustains a " frustule " exhibiting the 
front view, while the other is seen sideways. 

Another common diatom is shown in Fig. 23, 
and is known by the name of Synedra. This 
constitutes a very large genus, containing about 
seventy known species. In this genus the frustules 
are at first arranged upon a sort of cushion, but in 
course of time they mostly break away from their 
attachment. In some species they radiate in every 
direction from the cushion, like the spikes of the 
ancient cavalier's mace. 

Fig. 24 is another stalked diatom called Gompho- 
nema acuminatum, found commonly in ponds and 
ditches. There are nearly forty species belonging 
to this genus. A pair of frustules are also shown 
which exhibit the beautiful flinty outline without 
the coloured contents (technically called endo- 
chrome). 

Fig. 27 is a side view of a beautiful diatom, 
called Eunotia diadema from its diadem-like form. 
There are many species of this genus. When seen 
upon the upper surface, it looks at first sight like a 
mere row of cells with a band running along them ; 
but by careful arrangement of the light its true 
form may easily be made out. 

Fig. 28 represents a very common fresh- water 
diatom, named Melosi'ra varians. The plants of 
this genus look like a cylindrical rod composed of 
a variable number of segments, mostly cylindrical, 
but sometimes disc-shaped or rounded. An end 
view of one of the frustules is seen at the left hand, 



A NATURAL FIRE- ESC ATE 87 

still coloured with its dots of " endochrome," and 
showing the cylindrical shape. Immediately above 
is a figure of another frustule seen under both 
aspects with the endochrome removed. 

A rather curious species of diatom, called Coc- 
coneis pcdfculus, is seen at Fig. 29 as it appears 
on the surface of common water-cress. Sometimes 
the frustules, which in all cases are single, are 
crowded very closely upon each other and almost 
wholly hide the substance on which they repose. 
Fig. 30 is another diatom of a- flag-like shape, 
named Achnanthes, having a long slender filament 
attached to one end of the lower frustule, repre- 
senting the flag-staff. There are many wonderful 
species of such diatoms, some running almost end 
to end like a bundle of sticks, and therefore called 
Bacillaria ; others spreading out like a number of 
fans, such as the genus Licmophora ; while some 
assume a beautiful wheel-like aspect, of which the 
genus Meridion affords an excellent example. 

A very remarkable, and not uncommon, fresh- 
water diatom is the Bacillaria paradoxa. It 
looks, when at rest, like a broad brown ribbon of 
varying length. The diatoms lie across the ribbon, 
on edge, and slide upon each other exactly like the 
ladders of a fire-escape, so that the broad ribbon is 
converted into a fine long thread, which speedily 
closes up again into the original ribbon, and so da 
capo. The reason for this movement, and how it 
is effected, is absolutely unknown ; indeed, nothing 
certain is known as to the way in which diatoms 
move, nor has ever a probable guess yet been made, 



88 MOVING PLANTS 

The last of the diatoms which we shall be able 
to mention in this work is that represented on 
Fig. 31. The members of this genus have the 
name of Navieula, on account of their boat-like 
shape and their habit of gliding through the water 
in a canoe-like fashion. There are many species of 
this genus, all of which are notable for the graceful 
and varied courses formed by their outlines, and 
the extreme delicacy of their markings. In many 
species the markings are so extremely minute that 
they can only be made out with the highest powers 
of the microscope and the most careful illumination, 
so that they serve as test objects whereby the per- 
formance of a microscope can be judged by a 
practical man. 

The large spherical figure in the centre of Plate 
IV represents an example of a family belonging to 
the confervoid algae, and known by the name of 
Volvox globator. There seems to be but one 
species known. 

This singular plant has been greatly bandied 
about between the vegetable and animal king- 
doms, but seems now to be satisfactorily settled 
-among the vegetables. In the summer it may be 
found in pools of water, sufficiently large to be 
visible to the naked eye, like a little green speck 
proceeding slowly through the water. When a 
moderate power is used, it appears as shown in 
the figure, and always contains within its body a 
number of smaller individuals, which after a while 
burst through the envelope of the parent and start 



YEAST AND MOULDS 89 

upon mi independent existence. On a closer ex- 
amination, a further generation may be discovered 
even within the bodies of the children. The whole 
surface is profusely covered with little green bodies, 
each being furnished with a pair of movable cilia, 
by means of which the whole organism is moved 
through the water. These bodies are analogous to 
the zoospores already mentioned, and are connected 
with each other by a network of filaments. Re- 
production also takes place by conjugation as in 
other algoe. A more magnified representation of 
one of the green bodies is shown immediately above 
the larger figure. The volvox is apt to die soon 
when confined in a bottle. 

Fig. 25 is the common yeast-plant, consisting 
simply of a chain of cells, which increase by 
budding, and only form spores when they have 
exhausted the nutriment in the fluid in which they 
live. Fig. 26 is a curious object, whose scientific 
name is Sarcina ventriculi. It is found in the 
human stomach. Similar forms are often to be 
found in the air ; for instance, a piece of cocoa-nut 
will exhibit this, and many other kinds of Bacteria 
and moulds, after a few days' exposure to the air, 
preferably in a dark cupboard. 

We now come upon a few of the blights and 
mildews. A very interesting series of forms is 
first to be alluded to. Upon the bramble-leaf may 
often be found spots, at first red, then orange, 
then reddish black. These are known as CEcidium 
berberidis. Fig. 32 shows the "red-rust" of 
wheat, the Ure'do ; and Fig. 33 is the mildew of 



90 AL TERN A TION OF GENERA TIONS 

corn, known as Puccinia. The interest lies in the 
fact that these three forms are successive stages in 
the life-history of the same plant. Another species 
of Ur^do, together with a Phragmidium, once 
thought to be another kind of fungus, is seen on 
a rose-leaf on Plate V Fig. 1. On Fig. 10, 
however, of the same Plate, the Phragmidium may 
be seen proceeding from Uredo, thus proving them 
to be but two states of the 1 same plant. There is 
room for any amount of observation and work in 
connection with the life-histories of many of these 
fungi. 

Another species of Puccinia, found on the thistle, 
is shown on Plate V Fig. 7 Fig. 34 is the mould 
found upon decaying grapes, and called therefrom, 
or from the clustered spores, Botrytis. Some of 
the detached spores are seen by its side. Fig. 35 
is another species of the same genus, termed 
Botrytis parasitica, and is the cause of the well- 
known " potato-disease." 

The mosses and ferns afford an endless variety 
of interesting objects to the microscopist ; but as 
their numbers are so vast, and the details of their 
structure so elaborate, they can only be casually 
noticed in the present work. Fig. 38 represents 
a spore-case of the Polypodium, one of the ferns, 
as it appears while in the act of bursting and 
scattering the contents around. One of the spores 
is seen more magnified below. The spore-cases of 
many ferns may be seen bursting under the micro- 
scope, and have a very curious appearance, writhing 
and twisting like worms, and then suddenly filling 



MOSSES 91 

the field with a cloud of spores. Fig. 9, Plato V., 
is a piece of the brown, chaff-like, scaly structure 
found at the base of the stalk of male fern cells, 
showing the manner in which a flat membrane is 
formed. Fig. 39 is a capsule of the Hypnum, one 
of the mosses, showing the beautiful double fringe 
with which its edge is crowned. Fig. 2, Plate V., 
is the capsule of another moss, Polytri'chum, to 
show the toothed rim ; on the right hand is one 
of the teeth much more magnified. 

Fig. 3, Plate V., is the capsule of the Junger- 
mannia, one of the liverworts, showing the 
" elaters " bursting out on every side, and scatter- 
ing the spores. Fig. 4 is a single elater much 
magnified, showing it to be a spirally coiled 
filament, that, by sudden expansion, shoots out 
the spores just as a child's toy-gun discharges the 
arrow. Fig. 5 is a part of the leaf of the Sphag- 
num moss, common in fresh water, showing the 
curious spiral arrangement of secondary fibre 
which is found in the cells, as well as the circular 
pores which are found in each cell at a certain 
stage of growth. Just below, and to the left hand, 
is a single cell greatly magnified, in order to show 
these peculiarities more strongly. Fig. 8 is part 
of a leaf of Jungermannia, showing the dotted 
cells. 

Fig. 6, Plate V., is a part of a rootlet of moss, 
showing how it is formed of cells elongated and 
joined end to end. 

On the common mare's-tail, or Equisetum, may 
be seen a very remarkable arrangement for scatter- 



92 MARINE FORMS 

ing the spores. On the last joint of the stem is 
a process called a fruit-spike, being a pointed head 
around which are set a number of little bodies just 
like garden -tables, with their tops outward. One 
of these bodies is seen in Fig. 40. From the top 
of the table depend a number of tiny pouches, 
which are called sporangia ; these lie closely against 
each other, and contain the spores. At the proper 
moment these pouches burst from the inside, and 
fling out the spores, which then look like round 
balls with irregular surfaces, as shown in Fig. 40, c. 
This irregularity is caused by four elastic filaments, 
knobbed at the end, which are originally coiled 
tightly round the body of the spore, but by rapidly 
untwisting themselves cause the spore to leap 
about, and so aid in the distribution. A spore 
with uncoiled filaments is seen at Fig. 40, b. By 
breathing on them they may be made to repeat 
this process at will. 

Fig. 36 is a common little sea-weed, called 
Ectocarpus siliculosus, that is found parasitically 
adhering to large plants, and is figured in order 
to show the manner in which the extremities of 
the branches are developed into sporangia. Fig. 37 
is a piece of the common green laver, Ulva lafa's- 
sima, showing the green masses that are ultimately 
converted into zoospores, and by their extraordinary 
fertility cause the plant to grow with such rapid 
luxuriance wherever the conditions are favourable. 
Every possessor of a marine aquarium knows how 
rapidly the glass sides become covered with growing 
masses of this plant. The smaller figure above is a 



SEA- WEEDS 93 

section of the same plant, showing that it is com- 
posed of a double plate of cellular tissue. 

Fig. 41 is a piece of purple laver or "sloke," 
Porphyra laciniata, to show the manner in which 
the cells are arranged in groups of four, technically 
named " tetraspores." This plant has only one 
layer of cells. 

On Plate V may be seen a number of curious 
details of the higher algse. 

Fig. 11 is the Sphacelciria, so called from the 
curious capsule cells found at the end of the 
branches, and termed sphacehe. This portion of 
the plant is shown more magnified in Fig. 12. 
Another sea-weed is represented in Fig. 13, in 
order to show the manner in which the fruit is 
arranged ; and a portion of the same plant is given 
on a larger scale at Fig. 14. 

A very pretty little sea-weed called Ceramium 
is shown at Fig. 1 5 ; and a portion showing the 
fruit much more magnified is drawn at Fig. 22. 
Fig. 23 is a little alga called Myrionema, growing 
parasitically on the preceding plant. 

Fig. 1 6 is a section of a capsule belonging to the 
Halydris siliquosa, showing the manner in which 
the fruit is arranged ; and Fig. 1 7 shows one of 
the spores more magnified. 

Fig. 18 shows the Polysiphonia parasitica, a 
rather common species of a very extensive genus of 
sea-weeds, containing nearly three hundred species. 
Fig. 19 is a portion of the stem of the same plant, 
cut across in order to show the curious mode in 
which it is built up of a number of longitudinal 



94 REPRODUCTION OF SEA-WEEDS 

cells, surrounding a central cell of large dimensions, 
so that a section of this plant has the aspect of a 
rosette when placed under the microscope. A 
capsule or " ceramidium " of the same plant is 
shown at Fig. 20, for the purpose of exhibiting 
the pear-shaped spores, and the mode of their 
escape from the parent-cell previous to their own 
development into fresh plants. The same plant 
has another form of reproduction, shown in Kg. 21, 
where the " tetraspores " are seen imbedded in the 
substance of the branches. There is yet a third 
mode of reproduction by means of " antheridia," or 
elongated white tufts at the extremities of the 
branches. The cells produced by these tufts 
fertilise the rudimentary capsules, and so fulfil 
the function of the pollen in flowering plants. 

Fig. 25 is the Cladophora, a green alga, figured 
to illustrate its mode of growth ; and Fig. 2 6 
represents one of the red sea-weeds, Ptilota elegans, 
beautifully feathered, and with a small portion shown 
also on a larger scale, in order to show its structure 
more fully. A good contrast to this species is seen 
on Fig. 27, and the mode in which the long, slender, 
filamentary fronds are built up of many-sided cells 
is seen just to the left hand of the upper frond. 
Fig. 24 is a portion of the lovely Delesseria san- 
gui'nea, given in order to show the formation of 
the cells, as also the arrangement by which the 
indistinct nervures are formed. 

The figure on the bottom left-hand corner of 
Plate V is a portion of the pretty Mtophyllum 
laceratum, a plant belonging to the same family 



SEA-GRASS 95 

as the preceding one. The specimen here repre- 
sented has a gathering of spores upon the frond, 
iu which state the frond is said to be " in fruit." 

Fig. 27 represents a portion of the common sea- 
grass (Enlcromorpha), so common on rocks and 
stones between the range of high and low water. 
On the left hand of the figure, and near the top, 
is a small piece of the same plant much more 
magnified, in order to show the form of its cells. 



96 INSECTS 



CHAPTER VII 

Antennae, their Structure and Use — Eyes, Compound and 
Simple — Bretahing Organs— Jaws and their Appendages 
— Legs, Feet, and Suckers — Digestive Organs — Wings, 
Scales, and Hairs — Eggs of Insects — Hair, Wool, Linen, 
Silk, and Cotton — Scales of Fish — Feathers — Skin and 
its Structure — Epithelium — Nails, Bone, and Teeth — 
Blood Corpuscles and Circulation — Elastic Tissues — 
Muscle and Nerve. 

We now take leave of the vegetables for a time, 
and turn our attention to the animal kingdom. 

On Plate VI. may be seen many beautiful 
examples of animal structures, most of them 
being taken from the insect tribes. We will 
begin with the antennoe, or horns, as they are 
popularly termed, of the insect. 

The forms of these organs are as varied as those 
of the insects to which they belong, and they are 
so well defined that a single antenna will, in 
almost every instance, enable a good entomologist 
to designate the genus to which the insect belonged. 
The functions of the antennas are not satisfactorily 
ascertained. They are certainly often used as 
organs of speech, as may be seen when two ants 
meet each other, cross their antennae, and then 
start off simultaneously to some task which is too 



AN UNFORTUNATE INTRUDER 97 

much for a single ant. This pretty scene may be 
witnessed on any fine day in a wood, and a very 
animated series of conversations may readily be 
elicited by laying a stick across their paths, or 
putting a dead mouse or large insect in their 
way. 

I once saw a very curious scene of this kind 
take place at an ant's nest near Hastings. A 
great daddy long-legs had, unfortunately for itself, 
settled on the nest, and was immediately " pinned " 
by an ant or two at each leg, so effectually that 
all its struggles availed nothing. Help was, how- 
ever, needed, and away ran four or five ants in 
different directions, intercepting every comrade 
they met, and by a touch of the antennae sending 
them off in the proper direction. A large number 
of the wise insects soon crowded round the poor 
victim, whose fate was rapidly sealed. Every ant 
took its proper place, just like a gang of labourers 
under the orders of their foreman ; and by dint of 
pushing and pulling, the long-legged insect was 
dragged to one of the entrances of the nest, and 
speedily disappeared. 

Many of the ichneumon-flies may also be seen 
quivering their antennae with eager zeal, and evi- 
dently using them as feelers, to ascertain the 
presence of the insect in which they intend to lay 
their eggs ; and many other similar instances will 
be familiar to anyone who has been in the habit of 
watching insects and their ways. 

It is, however, most likely that the antennas 
serve other purposes than that which has just 
7 



9S Fr.YCr.WY OF AXTEXN.E 

been mentioned, ami many entomologists are of 
opinion that they swerve as organs of hearing. 

Fig. 15, 1'late VI., re- presents a part of one of 
the joints bel< 'Hiring to the antennae of the common 
huuse-ily ; it is .seen to be covered with a multi- 
tude of little depressions, some being small, and 
others very much larger. A section of the same 
nitenna, but on a larger scale, is shown by Fig. 16, 
in order to exhibit the real form of these depres- 
sions. Nerves have been traced to these curious 
cavities, which evidently serve some very useful 
purpose, some authors thinking them to belong to 
the sense of smell, and others to that of hearing. 
Perhaps they may be the avenues of some sensation 
not possessed by the human race, and of which we 
are therefore ignorant. Fig. 17 represents a sec- 
tion of the antennae of an ichneumon-fly, to show 
the structure of these organs of sense. 

We will now glance cursorily at the forms of 
antennae which are depicted in the Plate. 

Fig. 1 is the antenna of the common cricket, 
which consists of a vast number of little joints, 
each a trifle smaller than the preceding one, the 
whole forming a long, thread-like organ. Fig. 2 is 
taken from the grasshopper, and shows that the 
joints are larger in the middle than at either end. 

Figs. 3 and 5 are from two minute species of 
cocktailed beetles (Staphylinidce), which swarm 
throughout the summer months, and even in the 
winter may be found in profusion under stones 
and moss. The insect from which Fig 5 was 
taken is so small that it is almost invisible to the 



THEIR MODIFICATIONS 99 

naked eye, and was captured on the wing by- 
waving a sheet of gummed paper" under the shade 
of a tree. These are the tiresome little insects 
that so often get into the eye in the summer, and 
cause such pain and inconvenience until they are 
removed. 

Fig. 4 shows the antenna of the tortoise beetle 
(Cdssida), so common on many leaves, and remark- 
able for its likeness to the reptile from which it 
derives its popular name. Fig. 3 is from one of 
the weevils, and shows the extremely long basal 
joint of the antennas of these beetles, as well as 
the clubbed extremity. Fig. 7 is the beautifully 
notched antenna of the cardinal beetle (Pyrochrda), 
and Fig. 11 is the fan-like one of the common 
cockchafer. This specimen is taken from a male 
insect, and the reader will find his trouble repaid 
on mounting one of these antennas as a permanent 
object. 

Fig. 12 is an antenna from one of the common 
ground beetles (Cdrabus) looking like a string of 
elongated pears, from the form of the joints. The 
reader will see that in beetles he is sure to find 
eleven joints in the antennas. 

Fig. 10 is the entire antenna of a fly (Syrphus), 
one of those pretty flies which may be seen hover- 
ing over one spot for a minute, and then darting off 
like lightning to hang over another. The large 
joint is the one on which are found those curious 
depressions that have already been mentioned. 
Fig. 8 is one of the antennas of a tortoise-shell 
butterfly ( Vanessa), showing the slender, knobbed 



ioo MOTHS AND BUTTERFLIES 

form which butterfly antennae assume; and Figs. 
13 and 14 are' specimens of' moths' antennae, 
showing how they always terminate in a point. 
Fig. 13 is the beautiful feathery antenna of the 
ermine moth (Spilosdma) ; and Fig. 14 is the 
toothed one of the tiger moth (Arctia caja). In 
all these feathered and toothed antennae of moths, 
the male insects have them much more developed 
than the female, probably for the purpose of 
enabling them to detect the presence of their 
mates, a property which some possess in wonderful 
perfection. The male oak-egger moth, for example, 
can be obtained in any number by putting a female 
into a box with a perforated lid, placing the box 
in a room, and opening the window. In the course 
of the evening seven or eight males are seen to 
make their appearance, and they are so anxious to 
get at their intended mate that they will suffer 
themselves to be taken by hand. 

Fig. 9 is an antenna of the male gnat, a most 
beautiful object, remarkable for the delicate trans- 
parency of the joints, and the exquisitely fine 
feathering with which they are adorned. 

We now arrive at the eyes of the insects, all of 
which are very beautiful, and many singularly full 
of interest. 

In the centre of Plate IV may be seen the front 
view of the head of a bee, showing both kinds of 
eyes, three simple eyes arranged triangularly in the 
centre, and two large masses, compound eyes, at the 
sides. 

The simple eyes, termed " ocelli," are from one 



EYES, SIMPLE AND COMPOUND 101 

to three in number, and usually arranged in a 
triangular form between the two compound eyes. 
Externally they look merely like shining rounded 
projections, and can be seen to great advantage in 
the dragon - flies. The compound eyes may be 
considered as aggregations of simple eyes, set 
closely together, and each assuming a more or 
less perfect six-sided form. Their number varies 
very greatly ; in some insects, such as the common 
fly, there are about four thousand of these simple 
eyes in one compound one, in the ant only fifty 
in the dragon-fly about twelve thousand, and in 
one of the beetles more than twenty-five thousand. 

Fig. 18 shows a portion of the compound eye of 
the Atalanta butterfly, and Fig. 20 the same organ 
of the death's-head moth. A number of the pro- 
tecting hairs may be seen still adhering to the eye 
of the butterfly. Fig. 22 is a remarkably good 
specimen of the eye of a fly (Heliophilus), showing 
the facets, nearly square, the tubes to which they 
are attached, and portions of the optic nerves. 
Fig. 23 is part of the compound eye of a lobster, 
showing the facets quite square. All these draw- 
ings were taken by the camera lucida from my 
own preparations, so that I can answer for their 
authenticity. 

On Plate VIII. Figs. 6 and 12, the reader will 
find two more examples of eyes, these being taken 
from the spiders. Fig. 6 is an example of the 
eight eyes of the well-known zebra spider, so 
common on our garden walls and similar situa- 
tions, hunting incessantly after flies and other prey, 



102 BREATHING APPARATUS 

and capturing them by a sudden pounce. The 
eyes are like the ocelli of insects, and are simple 
in their construction. The number, arrangement, 
and situation of the eyes is extremely varied in 
spiders, and serves as one of the readiest modes of 
distinguishing the species. Fig. 12, Plate VIII., 
represents one of the curious eyes of the common 
harvest spider, perched on a prominence or 
" watch-tower " (as it has been aptly named), for 
the purpose of enabling the creature to take a more 
comprehensive view of surrounding objects. 

Keturning to Plate VI., in Pig. 12 we see a 
curiously branched appearance, something like the 
hollow root of a tree, and covered with delicate 
spiral markings. This is part of the breathing 
apparatus of the silkworm, extracted and prepared 
by myself for the purpose of showing the manner 
in which the tubes branch off from the " spiracle " 
or external breathing-hole, a row of which may be 
seen along the sides of insects, together with the 
beautiful spiral filament which is wound round 
each tube for the purpose of strengthening it. One 
of these spiracles may be seen in the neck of the 
gnat (Fig. 27). Another spiracle, more enlarged, 
may be seen on Plate VII. Fig. 34, taken from 
the wireworm, i.e. the larva of the skipjack beetle 
(Eldter), to show the apparatus for excluding dust 
and admitting air. The object of the spiral coil is 
very evident, for as these breathing-tubes extend 
throughout the whole body and limbs, they would 
fail to perform their office when the limbs were 



APHIDES 103 

bent, unless for some especial provision. This is 
achieved by the winding of a very strong but 
slender filament between the membranes of which 
the tube is composed, so that it always remains 
open for the passage of air throughout all the 
bends to which it may be subjected. Flexible 
tubes for gas and similar purposes are made after 
the same fashion, spiral metal wire being coiled 
within the india-rubber pipe. A little piece of 
this thread is seen unwound at the end of a small 
branch towards the top, and this thread is so strong 
that it retains its elasticity when pulled away from 
the tube, and springs back into its spiral form. 
I have succeeded in unwinding a considerable 
length of this filament from the breathing-tube of a 
humble bee. 

Fig. 2 8 represents the two curious tubercles upon 
the hinder quarters of the common green-blight, 
or Aphis, so very common on our garden plants, as 
well as on many trees and other vegetables. From 
the tips of these tubercles exudes a sweet colourless 
fluid, which, after it has fallen upon the leaves, is 
popularly known by the name of honey-dew. Ants 
are very fond of this substance, and are in the 
habit of haunting the trees upon which the aphides 
live, for the purpose of sucking the honey-dew as 
it exudes from their bodies. A drop of this liquid 
may be seen on the extremity of the lower tubercle. 

The head of the same insect may be seen in Fig. 
24, where the reader may observe the bright scarlet 
eye, and the long beak with which the aphis 
punctures the leaves and sucks the sap. Fig. 29 



104 BEETLES 

is the head of the sheep-tick, exhibiting the organ 
by which it pierces the skin of the creature on 
which it lives. Fig. 25 is the head of another 
curious parasite found upon the tortoise, and 
remarkable for the powerful hooked apparatus 
which projects in front of the head. 

Turning to Plate VII. Fig. 4, we find the head 
of a ground beetle (Cdrahcs), valuable as exhibit- 
ing the whole of the organs of the head and mouth. 

Immediately above the compound eyes are seen 
the roots of the antennas, those organs themselves 
being cut away. Above there are two pairs of 
similarly constructed organs termed the "maxillary 
palpi," because they belong to the lesser jaws or 
maxillae, seen just within the pair of great curved 
jaws called the mandibles, which are extended in so 
threatening a manner. The t: labial palpi," so called 
because they belong to the " labium," or under lip, 
are seen just within the others ; the tongue is seen 
between the maxillae, and the chin or " mentum " 
forms a defence for the base of the maxillae and 
the palpi. A careful examination of a beetle's 
mouth with the aid of a pocket lens is very instruct- 
ive as well as interesting. 

Fig. 1 on the same Plate shows the jaws of the 
hive bee, where the same organs are seen modified 
into many curious shapes. In the centre may be 
seen the tongue, elongated into a flexible and hair- 
covered instrument, used for licking the honey 
from the interior of flowers. At each side of the 
tongue are the labial palpi, having their outermost 
joints very small, and the others extremely large, 




VI. 



TONGURS OF INSECTS 105 

the latter acting as a kind of sheath for the tongue. 
Outside the labial palpi are the maxilke, separated 
in the specimen, but capable of being laid closely 
upon each other, and outside all are the mandibles. 

The curiously elongated head of the scorpion-fly 
(Panorjoa), seen at Fig. 7, affords another example 
of the remarkable manner in which these organs 
are developed in different insects. Another 
elongated head, belonging to the daddy long-legs, 
is seen in Plate VI. Fig. 27, and well shows 
the compound eyes, the antennae, and the palpi. 
Fig. 2 represents the coiled tongue of the Atalanta 
butterfly; it is composed of the maxillse, very 
greatly developed, and appearing as if each had 
originally be^en flat, and then rolled up so as to 
make about three-fourths of a tube. A number of 
projections are seen towards the tip, and one of 
these little bodies is shown on a larger scale at 
Fig. 3. These curious organs have -probably some 
connection with the sense of taste. Along the 
edges of the semi-tubes are arranged a number of 
very tiny hooks, by means of which the insect can 
unite the edges at will. 

Fig. 11, in the centre of the Plate, shows one of 
the most curious examples of insect structure, the 
proboscis or trunk of the common bluebottle-fly. 
The maxillary palpi covered with bristles are seen 
projecting at each side, and upon the centre are 
three lancet-like appendages, two small and one 
large, which are used for perforating various 
substances on which the insect feeds. The great 
double disc at the end is composed of the lower lip 



1 06 BLO W-FL VS PROBOSCIS 

greatly developed, and is filled with a most complex 
arrangement of sucking-tubes, in order to enable 
it to fulfil its proper functions. The numerous 
tubes which radiate towards the circumference are 
strengthened by a vast number of partial rings of 
strong filamentary substance, like that which we 
have already seen in the breathing-tube of the 
silkworm. Some of these partial rings are seen on 
Fig. 12, a little above. The mode in which the 
horny matter composing the rings is arranged 
upon the tubes is most wonderful, and requires a 
tolerably high power to show it. The fine hairs 
upon the proboscis itself afford most admirable 
practice for the young microscopist. They should, 
when properly lighted and focused, be quite black 
and sharp. Any errors of manipulation will cause 
them to be " fuzzy." 

Fig. 5 shows the tongue of the common cricket, 
a most elegantly formed organ, having a number of 
radiating bands covered with zigzag lines, due to 
the triangular plates of strengthening substance 
with which they are furnished, instead of the rings. 
A portion more highly magnified is shown at 
Fig. 6, exhibiting the manner in which the 
branches are arranged. 

The legs of insects now claim our attention. 

Fig. 9, Plate VII., shows the " pro-leg " of a 
caterpillar. The pro-legs are situated on the 
hinder parts of the caterpillar, and, being set in 
pairs, take a wonderfully firm hold of a branch or 
twig by pressure toward each other. Around the 



LEGS AND FEET 107 

pro-legs are arranged a series of sharp hooks, set 
with their points inwards, for greater power in 
holding. Fig. 10 represents one of the hooks more 
magnified. 

Fig. 15 is the lower portion of the many-jointed 
legs of the long-legged spider (Phaldngium), the 
whole structure looking very like the antenna of 
the cricket. Tig. 17 is the leg of the glow-worm, 
showing the single claw with which it is armed. 
Fig. 26 shows the foot of the flea, furnished with 
two simple claws. Fig. 16 is the foot of the 
Trombfdium, a genus of parasitic creatures, to 
which the well-known harvest-bug belongs. Fig. 
26, Plate VI., shows the leg of the green Aphis of 
the geranium, exhibiting the double claw, and the 
pad or cushion, which probably serves the same 
purpose as the pads found upon the feet of many 
other insects. Fig. 8 is the lower portion of the 
leg of the ant, showing the two claws and the 
curious pad in the centre, by means of which the 
insect is able to walk upon slippery surfaces. The 
Ti'pula has a foot also furnished with a single pad 
(see Plate VI. Fig. 30). This organ is seen under 
a very high power to be covered with long hair- 
like appendages, each having a little disc at the 
end, and probably secreting some glutinous fluid 
which will enable the creature to hold on to 
perpendicular and smooth surfaces. Many of my 
readers will doubtless have noticed the common 
fly, towards the end of autumn, walking stiffly 
upon the walls, and evidently detaching each foot 
with great difficulty, age and infirmity having made 



to8 FEET WITH SUCKERS 

the insect unable to lift its feet with the requisite 
force. 

Fig. 2 1 is the foot of one of the ichneumon-flies 
(Ophion), the hairy fringe being apparently for the 
purpose of enabling it to hold firmly to the cater- 
pillar in which it is depositing its eggs, and which 
wriggles so violently under the infliction that it 
would soon throw its tormentor had not some 
special means been provided f6r the purpose of 
enabling the latter to keep its hold. Fig. 20 is 
a beautiful example of a padded foot, taken from 
the little red parasitic creature so plentifully found 
upon the dor or dung beetle (Geotriipes), and of 
which the afflicted insect is said to rid itself by 
lying on its back near an ant's nest, and waiting 
until the ants carry off its tormentors. 

Fig. 18 is the foot of the common yellow dung- 
fly (plentiful in pasture lands), having two claws 
and two pads ; and Fig. 1 9 shows the three pads 
and two claws found in the foot of the hornet-fly 
(Asilus). 

Few microscopic objects call forth such general 
and deserved admiration as the fore-foot of the 
male water-beetle (Dytiscas), when properly pre- 
pared and mounted, for which see Fig. 13. 

On examining this preparation under the micro- 
scope, it is seen that three of the joints are greatly 
expanded, and that the whole of their under 
surface is covered profusely with certain wonderful 
projections, which are known to act as suckers. 
One of them is exceedingly large, and occupies 
a very considerable space, its hairs radiating like 



A WALKING DUST-BIN 109 

the rayB of the heraldic sun. Another is also 
large, but scarcely half the diameter of the former, 
and the remainder are small, and mounted on the 
extremities of delicate footstalks, looking something 
like wide-mouthed trumpets. In the specimen 
from which the drawing was taken the smaller 
suckers are well shown, as they protrude from the 
margin of the foot. 

One of the larger suckers is seen more magnified 
on Fig. 14. 

Plate VIII. Kg. 1, exemplifies the manner 
in which the muscles of insects do their work, 
being well attached in the limbs to the central 
tendon, and pulling " with a will " in one direction, 
thus giving very great strength. This leg is taken 
from the water boatman (Notonecta), and has been 
mounted in Canada balsam. 

On Plate VII. Pig. 29, may be seen a curiously 
formed creature. This is the larva of the tortoise 
beetle (Cdssida), the skin having been flattened 
and mounted in Canada balsam. The spiracles are 
visible along the sides, and at the end is seen a 
dark fork-like structure. This is one of the 
peculiarities of this creature, and is employed for 
the purpose of carrying the refuse of its food, 
which is always piled upon its back, and retained 
in its place by the forked spines, aided probably 
by the numerous smaller spines that project from 
the side. 

Fig. 33 shows part of the stomach and gastric 
teeth of the grasshopper. This structure may be 
seen to perfection in the " gizzard," as it is called, 



no WINGS 

of the great green locust of England (Acrida 
viridissima). The organ looks like a sudden swell- 
ing of the oesophagus, and when slit longitudinally 
under water, the teeth may be seen in rows set 
side by side, and evidently having a great grinding 
power. The common house cricket has a similar 
organ of remarkable beauty. Just above (Fig. 27) 
is the corresponding structure in the hive bee, 
three of the teeth being shown separately at 
Fig. 28. 

We now cast a rapid glance at the wings of 
insects. 

They have no analogy, except in their use, with 
the wings of birds, as they are not modifications of 
existing limbs, but entirely separate organs. They 
consist of two membranes united at their edges, 
and traversed and supported by sundry hollow 
branches or " nervures," which admit air, and serve 
as useful guides to entomologists for separating the 
insects into their genera. Indeed, the general 
character of the wings has long been employed as 
the means of dividing the insect race into their 
different orders, as may be seen in any work on 
entomology. The typical number of wings is four, 
but it often happens that two are almost wholly 
absent, or that the uppermost pair are thickened 
into a shelly kind of substance which renders them 
useless for flight ; while in many insects, such as 
the ground beetles and others, the upper wings 
become hardened into firm coverings for the body 
and the lower pair are shrivelled and useless. 



NERVATION OF WINGS in 

Fig. 22 shows two of the wings of a humble 
bee, together with their nervures, and the peculiar 
system by which the upper and lower pair are 
united together at the will of the insect. At the 
upper edge of the lower wing, and nearly at its 
extremity, may be seen a row of very tiny hooks, 
shown on a larger scale at Fig. 25. These hooklets 
hitch into the strengthened membrane of the upper 
wing, which is seen immediately above them, and 
so conjoin the two together. The curious wing- 
hooks of the Aphis may be seen on Fig. 24, very 
highly magnified. 

Fig. 31 is the wing of the midge {Psychoda), 
that odd little insect which is seen hopping and 
popping about on the windows of outhouses and 
similar localities, and is so hard to catch. The 
whole wing is plentifully covered with elongated 
scales, and is a most lovely object under any power 
of the microscope. These scales run along the 
nervures and edges of the wings, and part of a 
nervure is shown more highly magnified at 
Fig. 32*. 

At Fig. 23 is shown the wing of one of the 
hemipterous insects, common along the banks of 
ditches and in shady lanes, and known by the 
name of Ci'xius. It is remarkable for the numer- 
ous spots which stud the nervures, one being always 
found at each forking, and the others being very 
irregularly disposed. 

Fig. 30 is one of the balancers or "halteres" of 
the house-fly. These organs are found in all the 
two-winged insects, and are evidently modifications 



112 BALANCERS 

of the second pair of wings. They are covered 
with little vesicles, and protected at their base by 
scales. Some writers suppose that the sense of 
smell resides in these organs. Whatever other 
purpose they may serve, they clearly aid in the 
flight, as, if the insect be deprived of one or both 
of the balancers, it has the greatest difficulty in 
steering itself through the air. 

The wings of insects are mostly covered with 
hairs or scales, several examples of which are given 
in Plate VIII. Fig. 4 shows one of the scales of 
the Adippe or fritillary butterfly, exhibiting the 
double membrane — part of which has been torn 
away — and the beautiful lines of dots with which 
it is marked. The structure of the scales is further 
shown by a torn specimen of tiger moth scale 
seen on Fig. 16. On many scales these dots 
assume a " watered " aspect when the focus or 
illumination changes, an example of which may be 
seen in Fig. 15, a scale of the peacock butterfly. 

Fig. 1 1 is one of the ordinary scales of the azure 
blue butterfly, and Fig. 1 shows one of the curious 
" battledore " scales of the same insect, with its 
rows of distinct dottings. Fig. 14 is one of .the 
prettily tufted scales of the orange-tip butterfly, 
and Fig. 8 is the splendid branched scale of the 
death's-head moth. Fig. 19 shows a scale of the 
sugar-runner (Lepisma saccharina), a little silvery 
creature with glistening skin, and long bristles at 
the head and tail, that is found running about 
cupboards, window-sills, and similar places. It is 
not easy to catch With tne fingers, as it slips 







VII. 



SCALES 113 

through them like oil; but by holding a cover-glass 
in a pair of forceps, and pressing it upon one of 
the little creatures, a number of the scales may be 
caused to adhere to it, and these should be mounted 
dry for examination. The gnats also possess very 
pretty scales, with the ribs projecting beyond the 
membrane. 

Fig. 21 is a scale from the common spring- tail 
{Podura plumbea), a little creature which is found 
plentifully in cellars and other damp places, skip- 
ping about with great activity. Some flour scattered 
on a piece of paper is a sure trap for these little 
beings. Fig. 3 is one of the scales taken from the 
back of the celebrated diamond beetle, showing 
the cause of the magnificent gem-like aspect of 
that insect. We have in England many beetles of 
the same family — the weevils — which, although 
much smaller, are quite as splendid when exhibited 
under a microscope by reflected light. The wing- 
case or " elytron " of a little green weevil, very 
common in the hedges, may be seen on Plate XII. 
Fig. 10. 

The reader will observe that all these scales are 
furnished with little root-like appendages, by means 
of which they are affixed to the insect. Fig. 13 
shows a portion of the wing of the azure blue 
butterfly, from which nearly all the scales have 
been removed, for the purpose of exhibiting the 
pits or depressions in which they had formerly 
been fastened, and one or two of the scales are 
left still adherent to their places. The scales are 
arranged in equal rows like the slates of a housetop, 
8 



114 EGGS 

as may be seen on Fig. 18, which represents part 
of the same wing, to show the scales overlapping 
each other, and the elegant form which they take 
near the edges of the wing, so as to form a delicate 
fringe. The long hair-like down which covers the 
legs and bodies of the moths and butterflies (which 
are called Lepidoptera, or scale-winged insects, in 
consequence of this peculiarity), is seen under the 
microscope to be composed of scales very much 
elongated, as is shown in Fig. 17, a portion taken 
from the leg of a tiger moth. 

The eggs of insects are all very beautiful, and 
three of the most curious forms are given on 
Plate VIII. 

Fig. 2 is the empty egg of the gad-fly, as it 
appears when fastened to a hair of the horse. 
Fig. 5 represents the pretty ribbed egg of the 
common tortoise-shell butterfly ; and Fig. 7 is 
the very beautiful egg of the very horrid bed-bug, 
worthy of notice on account of the curious lid 
with which its extremity is closed, by means of 
which the young larva creeps out as soon as it is 
hatched. 

The feathers of birds, and the fur of animals, 
will furnish many examples of the eggs of parasites, 
some of which are of extreme beauty. The feather 
or hair may be mounted in a cell without disturb- 
ing the eggs, which should, however, be heated 
sufficiently to kill the embrj^o if present. 

Fig. 9 shows the penetrating portions of the stin^ 
of the wasp. The two barbed stings, which seem 



STINGS 115 

to be the minute prototypes of the many-barbed 
spears of the South Sea islanders, are seen lying 
one at each side of their sheath, and a single barb 
is drawn a little to the left on a very much larger 
scale. It is by reason of these barbs that the 
sting is always left adhering to the wound, and is 
generally drawn wholly out of the insect, causing 
its death in a short while. 

The sting is only found in female insects, and is 
supposed to be analogous to the " ovipositor " of 
other insects, i.e. the instrument by which the 
eggs are deposited in their places. Fig. 20 shows 
the curious egg-placing apparatus of one of the 
saw-flies. The backs of these " saws " work in 
grooves, and they work alternately, so that the 
fly takes but a very short time in cutting a slit 
in the young bark of a tender shoot, and laying 
her eggs in the slit. When she has completed 
one of these channels, she sets to work upon 
another, and in the early spring the young branches 
of the gooseberry bushes may be seen plentifully 
covered with these grooves and the eggs. When 
hatched, black caterpillar-like grubs from the eggs 
issue, and devastate the bushes sadly, turning in 
process of time into blackish flies, which are seen 
hovering in numbers over the gooseberries, and may 
be killed by thousands. 

The scales and hairs of other animals deserve 
great attention. Fig. 23 is a single hair of the 
human beard, as it often appears when tied in a 
knot — by Queen Mab and her fairies, according 



Ii6 HAIR AND WOOL 

to Mercutio. Fig. 22 is a portion of the same 
hair as it appears when splitting at its extremity. 
The structure of the hair is not, however, so well 
seen in this object as in that represented on Fig. 
24, which is a beautiful example of white human 
hair that once adorned the head of the victor of 
Waterloo. It formed one of a tiny lock given to 
me by a friend, and is so admirable an example of 
human hair, that I forthwith mounted it for the 
microscope. In this hair the cells may be seen 
extending down its centre, and the peculiar 
roughened surface produced by the flattened cells 
which are arranged around its circumference are 
also seen. By steeping in caustic potash, these 
scales can be separated, but generally they lie 
along the hair in such a manner that if the hair 
be drawn through the fingers from base to point, 
their projecting ends permit it to pass freely; 
whilst if it be drawn in the reverse direction, they 
cause it to feel very harsh to the touch. 

In the sheep's wool (Fig. 30) this structure is 
much more developed, and gives to the fibres the 
"felting" power that causes them to interlace so 
firmly with each other, and enables cloth — when 
really made of wool — to be cut without unravelling. 
Fig. 3 7 is the smooth hair of the badger ; and 
Fig. 34 is the curious hair of the red deer, which 
looks as if it had been covered with a delicate 
net. 

Fig. 28 is the soft, grey, wool-like hair of the 
rat; and Fig. 29 is one of the larger hairs that 
protrude so plentifully, and form the glisteninw 



FJBKES 117 

brown coat of that animal. Fig. 3 8 is the curiously 
knobbed hair of the long-eared bat, the knobs 
being formed of protuberant scales that can easily 
be scraped off. Fig. 31 shows a hair of the 
common mole; and Fig. 32 is one of the long 
hairs of the rabbit. Fig. 27 is a flat hair of the 
dormouse, slightly twisted, the difference in the 
breadth showing where the twist has taken place. 
The hair of the mouse is beautifully ribbed, so as 
to look like a ladder. Fig. 26 is one of the very 
long hairs that so thickly clothe the tiger moth 
caterpillar; and Fig. 25 is a beautifully branched 
hair taken from the common humble bee. 

All hairs should be examined by polarised light, 
with a plate of selenite, when most gorgeous colour 
effects may be obtained. 

The four fibres mostly used in the manufacture 
of apparel are: wool, Fig. 30, which has already 
been described; linen, Fig. 39; cotton, Fig. 40; 
and silk, Fig. 41. The structure of each is very 
well marked and easily made out with the micro- 
scope ; so that an adulterated article can readily 
be detected by a practised eye. Cotton is the 
most common adulteration of silk and linen fabrics, 
and may at once be detected by its flat twisted 
fibre. Silk is always composed of two parallel 
threads, each proceeding from one of the spinnerets 
of the caterpillar, and it may be here remarked 
that if these threads are not quite parallel the silk 
is of bad quality. Silken fibre is always covered, 
when new, with a kind of varnish, usually of a 
bright orange colour, which gives the undressed 



u8 FISH-SCALES 

" floss " silk its peculiar hue, but which is soluble 
and easily washed away in the course of manu- 
facture. 

Figs. 35 and 36 are the small and large hairs of 
that magnificent creature, the sea mouse {Aphrodite 
aculedta), whose covering, although it lies in the 
mud, glows with every hue of the rainbow, and in 
a brilliant light is almost painfully dazzling to the 
eye. 

The scales of some of the fishes are shown on 
Plate VIII., in order to exhibit their mode of 
growth by successive layers. The scales are always 
enveloped in membranous sacs, and in some cases, 
as in the eel, they do not project beyond the 
surface, and require some little observation to 
detect them. A scale of an eel is shown on Plate 
XL Fig. 15, and is a magnificent object under 
polarised light. Fig. 33 is a scale of the greenbone 
pike ; and Figs. 42 and 43 are scales of the perch, 
showing the roots by which they are held in their 
places. The roach, dace, bleak, and many other 
similar fish have a beautiful silvery substance on 
the under surface of the scales, which was greatly 
used in the manufacture of artificial pearls, glass 
beads being thinly coated in the interior with the 
glittering substance, and then filled in with wax. 
A piece of sole-skin, when preserved in Canada 
balsam and placed under the microscope, is a very 
beautiful object. 

More examples of hairs, and other processes 
from the skin, together with the structure of the 



FEATHERS 1 19 

Bkin itself, of bone, of blood, and the mode in 
which it circulates, are given on Plate X. 

In all important points of their structure the 
feathers of birds are similar to the hairs of animals, 
and are developed in a similar manner. They are 
all composed of a quill portion, in which the pith 
is contained, and of a shaft, which carries the vane, 
together with its barbs. The form of each of these 
portions varies much, even in different parts of the 
same bird, and the same feather has almost always 
two kinds of barbs ; one close and firm, and the 
other loose, floating, and downy. If a small feather 
be plucked from the breast or back of a sparrow or 
any other small bird, the upper part of the feather 
is seen to be close and firm, while the lower is 
loose and downy, the upper part being evidently 
intended to lie closely on the body and keep out 
the wet, while the lower portion affords a soft and 
warm protection to the skin. 

Fig. 12, Plate X., shows the feather of a peacock, 
wherein the barbs are very slightly fringed and lie 
quite loosely side by side. Pig. 18 is part of 
the same structure, in a duck's feather, wherein 
are seen the curious hooks which enable each 
vane to take a firm hold of its neighbour, the 
whole feather being thus rendered firm, compact, 
and capable of repelling water. The reader will 
not fail to notice the remarkable analogy between 
these hooks and those which connect the wings of 
the bee. 

Fig. 17 is a part of the shaft of a young feather 
taken from the canary, given for the purpose of 



120 SECTION'S OF HAIR 

showing the form of the cells of which the pith 
is composed. Fig. 20 is part of the down from a 
sparrow's feather, showing its peculiar structure; 
and Fig. 2 1 is a portion of one of the long drooping 
feathers of the cock's tail. 

Fig. 13 exhibits a transverse section of one of 
the large hairs or spines from the hedgehog, and 
shows the disposition of the firm, horn-like exterior, 
and the arrangement of the cells. Sections of 
various kinds of hair are interesting objects, and 
are easily made by tying a bundle of them together, 
soaking them in gum, hardening in spirit, and then 
cutting thin slices with a razor. A little glycerine 
will dissolve the gum, and the sections of hair will 
be well shown. Unless some such precaution be 
taken, the elasticity of the hair will cause the tiny 
sections to fly in all directions, and there will be 
no hope of recovering them. 

Several examples of the skin are also given. 
Fig. 27 is a section through the skin of the human 
finger, including the whole of one of the little 
ridges which are seen upon the extremity of every 
finger, and half of two others. The cuticle, epi- 
dermis, or scarf-skin, as it is indifferently termed, 
is formed of cells or scales, much flattened and 
horny in the upper layers, rounder and plumper 
below. The true skin, or " cutis," is fibrous in 
structure, and lies immediately beneath, the two 
together constituting the skin, properly so called. 
Beneath lies a layer of tissue filled with fatty 
globules, and containing, the glands by which the 
perspiration is secreted 



SA'/JV .-LVD ITS GLANDS 121 

One of the tubes or channels by which these 
glands are enabled to pour their contents to the 
outside of the body, and, if they be kept perfectly 
clean, to disperse them into the air, is seen running 
up the centre of the figure, and terminating in a 
cup-shaped orifice on the surface of the cuticle. 
On the palm of the hand very nearly three thou- 
sand of these ducts lie within the compass of a 
square inch, and more than a thousand in every 
square inch of the arm and other portions of the 
body, so that the multitude of these valuable 
organs may be well estimated, together with the 
absolute necessity for keeping the skin perfectly 
clean in order to enjoy full health. 

Fig. 1 shows a specimen of epidermis taken from 
the skin of a frog, exhibiting the flattened cells 
which constitute that structure, and the oval or 
slightly elongated nuclei, of which each cell has 
one. In Fig. 32, a portion of a bat's wing, the 
arrangement of the pigment is remarkably pretty. 
Immediately above, at Fig. 31, is some of the 
pigment taken from the back of the human eye- 
ball. The shape of the pigment cells is well 
shown. Similar specimens may easily be obtained 
from the back of a sheep's eye which has been hard- 
ened in spirit, or from that of a boiled fish. Fig. 
3 3 shows the pigment in the shell of the prawn. 

On various parts of animal structures, such as 
the lining of internal cavities, the interior of the 
mouth, and other similar portions of the body, the 
cells are developed into a special form, which is 



t22 EPITHELIUM 

called " Epithelium," and which corresponds to the 
epidermis of the exterior surface of the body. The 
cells which form this substance are of different 
shapes, according to their locality. On the tongue, 
for example (for which see Fig. 11), they are 
flattened, and exhibit their nucleus, in which the 
nucleolus may be discovered with a little care. 
Cells of this kind are rounded, as in the case just 
mentioned, or angular, and in either case they are 
termed squamous (i.e., scaly) epithelium. Sometimes 
they are like a number of cylinders, cones, or 
pyramids, ranged closely together, and are then 
called cylindrical epithelium. Sometimes the free 
ends of cylindrical epithelium are furnished with a 
number of vibrating filaments or cilia, and in this 
case the structure is called " ciliated " epithelium. 
Cylindrical epithelium may be found in the ducts 
of the glands which open into the intestines, as 
well as in the glands that secrete tears ; and 
ciliated epithelium is seen largely in the windpipe, 
the interior of the nose, etc. A specimen taken 
from the nose is seen at Fig. 15. A beautiful 
example of ciliated epithelium is to be found in 
the gills of the mussel. A portion of one of the 
yellowish bands which lie along the edge of the 
shell on the opening side is carefully removed 
with sharp scissors, and examined in the shell- 
liquor, being protected from pressure by placing 
a piece of paper beneath each end of the cover- 
glass. Such a preparation is shown in Plate IX. 
Fig. 39, but no drawing can give an idea of its 
wonderful beauty and interest. The cilia will 



BONE 123 

continue to move for a long time after removal 
from the shell. 

Bone in its various stages is figured on Plate X. 

Fig. 9 is a good example of human bone, and is 
a thin transverse section taken from the thigh. 
When cut across, bone exhibits a whitish structure 
filled with little dottings that become more numer- 
ous towards the centre, and are almost invisible 
towards the circumference. In the centre of the 
bone there is a cavity, which contains marrow in 
the mammalia and air in the birds. When placed 
under a microscope, bone presents the appearance 
shown in the illustration. 

The large aperture in the centre is one of innu- 
merable tubes that run along the bone and serve 
to allow a passage to the vessels which convey blood 
from one part of the bone to another. They are 
technically called Haversian canals, and if a longi- 
tudinal section be made they will be found running 
tolerably parallel, and communicating freely with 
each other. Around each Haversian canal may be 
seen a number of little black spots with lines 
radiating in all directions, and looking something 
like flattened insects. These are termed bone-cells 
or "lacunae," and the little black lines are called 
" canalfculi." In» the living state they contain cells 
which are concerned in the growth of the bone, and 
these may be made evident by softening fresh bone 
with acid, cutting sections of it, and staining. 
When viewed by transmitted light the lacunas and 
canaliculi are black ; but when seen by dark-field 



124 DEVELOPMENT OF BONE 

illumination the Haversian canals become black, 
and the lacunae are white. 

As these canaliculi exist equally in every direc- 
tion, it is impossible to make a section of bone 
without cutting myriads of them across ; and when 
a high power is employed they look like little dots 
scattered over the surface. A very pretty object 
can be made of the bone taken from a young animal 
which has been fed with madder, as the colour gets 
into the bone and settles chiefly round the Haver- 
sian canal. A young pig is a very good subject, so 
is a rabbit. 

Fig. 1 6 is a similar section cut from the leg-bone 
of an ostrich. 

The development of bone is beautifully shown in 
Fig. 30, 'c delicate slice taken from a pig's rib. 
Above may be seen the gristle or cartilage, with the 
numerous rows of cells ; below is the formed bone, 
with one of the Haversian canals and its contents ; 
while between the two may be seen the cartilage- 
cells gathering together and arranging themselves 
into form. The cartilage-cells are well shown in 
Fig. 28, which is a portion of the cup which had 
contained the eye of a haddock. 

The horn-like substances at the end of our fingers, 
which we call the nails, are composed of innumerable 
flattened cells. These cells are generally so fused 
together as to be quite indistinguishable even with 
a microscope, but can be rendered visible by soaking 
a section of nail in liquor potassae, which causes the 
cells to swell up and resume to a degree their 
original rounded form. 



TEETH 135 

It is worthy of remark that the animal form is 
built up of cells, as is the case with the vegetables, 
although the cells are not so variable in shape. 
They generally may be found to contain well-marked 
nuclei, two or more of the latter being often found 
within a single cell, and in many cases the tiny 
nucleoli are also visible. Good examples of these 
cells may be obtained from the yolk of an egg, and 
by careful management they may be traced through- 
out every part of the animal form. 

The teeth have many of the constituents of bone, 
and in some of their parts are made after precisely 
the same fashion. When cut, the teeth are seen to 
consist of a hard substance, called enamel, which 
coats their upper surfaces, of dentine, or ivory, 
within the enamel, and of " cement," which sur- 
rounds the fangs. In Fig. 26, Plate X., which is 
a longitudinal section of the human " eye " tooth, is 
seen the ivory occupying the greater part of the 
tooth, coated by the enamel at the top and the 
cement at the bottom. In the centre of each tooth 
there is a cavity, which is plentifully filled with a 
pulpy substance by which the tooth is nourished, 
and which conveys the nerves which endow it with 
sensation. A traverse section of the same tooth is 
seen in Fig. 25. 

The enamel is made of little elongated prisms, all 
pointing to the centre of the tooth. When viewed 
transversely, their ends are of a somewhat hexagonal 
shape, something like an irregular honeycomb. The 
dentine is composed of a substance pierced with 
myriads of minute tubes. They require a rather 



126 ELASTIC TISSUE 

high power — say 300 diameters — to show them 
properly. The cement is found at the root of the 
fangs, and is best shown in the tooth of an aged 
individual, when it assumes very clearly the char- 
acter of bone. 

Sections may be made by sawing a slice in the 
required direction, polishing one side, and cementing 
it with old Canada balsam to a slide. It may then 
be filed down to nearly the required thinness, 
finished by carefully rubbing with a hone, and 
polished with buff leather. Canada balsam may 
then be dropped upon it, and a glass cover pressed 
firmly down. 

Sections of young bone form magnificent objects 
for the polariser. 

Fig. 29 is a section cut from one of the palate 
teeth of the ray (Mylidb&tes). 

A rather important element in the structure of 
animals is the " elastic ligament," which is found 
in the back of the neck and other parts of the body, 
especially about the spine. It is made of a vast 
number of fibres of variable shape and length, 
branching and communicating, arranged generally 
in bundles, and remarkable for containing very few 
vessels, and no nerves at all. At Fig. 14 may be 
seen an example of elastic ligament, popularly called 
" paxwax," taken from the neck of a sheep. 

The white fibrous tissue by which all the parts 
of the body are bound together is seen at Fig. 1 ; 
and at Fig. 11 is a beautiful example of the 
" ultimate fibres " of the crystalline lens of a 
sturgeon's eye. 



MUSCLE AND NERVE 127 

The muscles of animals are of two kinds, the one 
termed the striped, and the other the unstriped. 
Of these, the latter belongs to organs which work- 
independently of will, such as the stomach, etc., 
while the former belongs to those portions of the 
body which are subject to voluntary motion, such 
as the arm and the leg. The unstriped muscle is 
very simple, consisting merely of long spindle-shaped 
cells, but the striped or voluntary muscle is of more 
complex construction. Every voluntary muscle 
consists of myriads of tiny fibres, bound together in 
little bundles, enveloped in a kind of sheath. 
Fig. 24 is an example of this muscular fibre, taken 
from beef. When soaked in spirit, it often splits 
into a number of discs, the edges of which are 
marked by the transverse lines. 

A fibre of nerve is drawn at Fig. 23, and is given 
for the purpose of showing the manner in which the 
nerve is contained in and protected by its sheath, 
just like a telegraph-wire in its coverings. Just 
above is a transverse section of the same fibre, 
showing the same arrangement from another point 
of view, and also illustrating the curious pheno- 
menon, that when nerve-fibres are treated with 
carmine the centre takes up the colouring matter, 
while the sheath remains white as before. The 
best way of studying nerves is to decapitate a frog, 
and cut off a piece of one of the nerves, which, like 
fine silk threads, come out between the joints of the 
spine inside the abdomen. By careful teasing out 
it is easy to obtain preparations showing all the 
above points, and, in addition, the folding-in of the 



128 BLOOD 

internal sheath which correspond to the insulators 
of a telegraph-line. 

The blood of animals is analogous in its office to 
the sap of plants, but differs greatly from it under 
the microscope. In sap there seem to be no 
microscopic characters, except that when a branch 
is cut, as in the vine, the flowing sap may contain 
certain substances formed in the wounded cells, such 
as chlorophyll, starch, and raphides ; but the blood 
is known to be an exceedingly complex substance 
both in a microscopic and a chemical point of view. 
When a little fresh blood is placed under the 
microscope, it is seen to consist of a colourless fluid 
filled with numerous little bodies, commonly called 
" blood-globules," varying very greatly in size and 
shape, according to the animal from which they 
were taken. Those of the reptiles are very large, 
as may be seen at Fig. 4, Plate X., which represents 
a blood corpuscle of the Proteus. In this curious 
reptile the globules are so large that they may be 
distinguished during its life by means of a common 
pocket lens. 

In the vertebrated animals these corpuscles are 
red, and give to the blood its peculiar tint. They 
are accompanied by certain colourless corpuscles, 
spherical in form, which are sometimes, as in man, 
larger than the red globules, and in others, as in the 
siren and the newt, considerably smaller. The 
general view of the red corpuscles has sufficient 
character to enable the practised observer to name 
the class of animal from which it was taken, and in 
some cases they are so distinctive that even the 



BLOOD CORPUSCLES 129 

genus can be ascertained with tolerable certainty. 
In point of size, the reptiles have the largest and 
the mammalia the smallest, those of the Proteus 
and the musk-deer being perhaps the most decidedly 
opposed to each other in this respect. 

In shape, those of the mammalia are circular 
discs, mostly with a concave centre, though the 
camel has oval ones ; those of the birds are more 
or less oval and convex ; those of the reptiles are 
decidedly oval, very thin, and have the nucleus 
projecting; and those of the fishes are oval and 
mostly convex. During the process of coagulation 
the blood corpuscles run together into a series of 
rows, just as if a heap of pence had been piled on 
each other and then pushed down, so that each 
penny overlaps its next neighbour. 

These objects are illustrated by six examples on 
Plate X. Fig. 2 is human blood, showing one of 
the white corpuscles ; Fig. 3 is the blood of the 
pigeon ; Fig. 4, of the Proteus anguinus ; Fig. 5, of 
the tortoise; Fig. 6, of the frog, showing the pro- 
jecting nucleus; and Fig. 7, of the roach. The 
blood possesses many curious properties, which can- 
not be described in these few and simple pages. 

In the centre of Plate X. is a large circular figure 
representing the membrane of a frog's foot as seen 
through the microscope, and exhibiting the circula- 
tion of the blood. The mode of arranging the foot 
so as to exhibit the object without hurting the frog 
is simple enough. 

Take an oblong slip of wood, — my own was made 
in five minutes out of the top of a cigar-box, — bore a 
9 



1 3 o CIRCULATION TN THE FROG 

hole about an inch in diameter near one end, and 
cut a number of little slits all round the edge of the 
wooden slip. Then get a small linen bag, put the 
frog into it, and dip him into water to keep him 
comfortable. When he is wanted, pull one of his 
hind feet out of the bag, draw the neck tight 
enough to prevent him from pulling his foot back 
again, but not sufficiently tight to stop the circula- 
tion. Have a tape fastened to the end of the bag, 
and tie it down to the wooden slide. Then fasten 
a thread to each of his toes, bring the foot well over 
the centre of the hole, stretch the toes well apart, 
and keep them in their places by hitching the 
threads into the notches on the edge of the wooden 
strip. Perhaps an easier plan is to secure the 
threads by drops of sealing-wax when in the desired 
position. Push a glass slide carefully between the 
foot and the wood, so as to let the membrane rest 
upon the glass, and be careful to keep it well wetted. 
If the frog kick, as he will most likely do, pass a 
thin tape over the middle of the leg, and tie him 
gently down to the slide. 

Bring the glass into focus, and the foot will 
present the , appearance so well depicted in the 
engraving. The veins and arteries are seen spread- 
ing over the whole of the membrane, the larger 
arteries being often accompanied by a nerve, as seen 
in the illustration. Through all these channels the 
blood continually pours with a rather irregular 
motion, caused most probably by the peculiar 
position of the reptile. It is a most wonderful 
sight, of which the observer is never tired, and 



FISHTAILS AND TADPOLES iji 

which seems almost more interesting every time 
that it is heheld. 

The corpuscles go pushing and jostling one 
another in the oddest fashion, just like a British 
crowd entering an exhibition, each one seeming to 
be elbowing its way to the best place. To see them 
turning the corners is very amusing, for they always 
seem as if they never could get round the smaller 
vessels, and yet invariably accomplish the task with 
perfect ease, turning about and steering themselves 
as if possessed of volition, and insinuating their 
ends when they could not pass crosswise. 

By putting various substances, such as spirit or 
salt, upon the foot, the rapidity of the circulation 
at the spot can be greatly increased or reduced at 
will, or even stopped altogether for a while, and the 
phenomenon of inflammation and its gradual natural 
cure be beautifully illustrated. The numerous black 
spots upon the surface are pigment-cells. 

The tails of young fish also afford excellent objects 
under the microscope, as the circulation can be seen 
nearly as well as in the frog's foot. The gills of 
tadpoles can also be arranged upon the stage with 
a little care, and the same organs in the young of the 
common newt will also exhibit the circulation in a 
favourable manner. The frog, however, is perhaps 
the best, as it can be arranged on the " frog-plate " 
without difficulty, and the creature may be kept for 
months by placing it in a cool, damp spot, and 
feeding it with flies, little slugs, and similar 
creatures. 



i3a POND- LI SB 



CHAPTER VIII 

Pond-Life — Apparatus and Instructions for Collecting Objects 
— Methods of Examination — Sponge — Infusoria. 

Of all departments of microscopic research the 
most fascinating and the most popular is that 
which deals with what is known by the generic 
name of " pond-life." The minute forms of the 
animal creation included in this term are of such 
exquisite beauty, and allow the processes of their 
life-history to be followed with such facility, from 
the cradle (when they have one) to the grave 
(which is very often the body of another, larger, 
organism), that there is none which has attracted 
more observers. Indeed, the first application of 
the microscope, by Leeuwenhoek, early in the 
seventeenth century, was to the observation of 
these forms of life. 

A few words may be said, in the first place, as 
to the outfit. A very useful part of it is a walking- 
stick, to which can be attached either a net for 
capturing the larger forms of life, or a hook for 
collecting the weeds, to which many forms of great 
interest and beauty are attached (Fig. 15). The 
stick is telescopic, and can also have attached to it 
a bottle, which, put into the water at any desired 




IX 



APPLIANCES FOR CO 1. 1 ECT1NG 



133 



spot,— say, amongst a clump of weeds, or near the 
bottom, upside down, and then suddenly reversed, 
— will bring away samples of the inhabitants of 
the neighbourhood. When these are sparsely dis- 
tributed through the water, the latter may be con- 
centrated by the use of a bottle round the neck of 
which is firmly tied a coarse calico bag, funnel- 
shaped, and supported by a wire ring, somewhat as 
shown in the illustration. Muslin is, however, too 




Fig. 15. 

coarse for many organisms. This net is immersed 
in the water so that the ring is just above the 
surface, and one bottleful after another poured 
through. The water strains off, the organisms are 
left behind. The immersion is necessary to reduce 
the pressure to which delicate organisms would 
otherwise be subjected. When the bottle is full, 
or sufficiently concentrated as to its contents, the 
latter are poured into one of the ordinary collect- 
ing-bottles, of which half a dozen at least should 
always be taken. 



M4 SELECTING ORGANISMS 

On reaching home, and as often as possihle on 
the way, the corks should be removed, as these 
organisms soon use up the air in the water. 

For examination a glass trough of considerable 
size, say three inches in length, half an inch in 
depth, and two inches in height, should be half 
filled with the water, and examined with the pocket 
magnifier. "With a little practice it will be found 
easy to take up not only the larger organisms, but 
even very minute ones, with one of the dipping- 
tubes with a long tapering point already referred 
to. The organism, when " spotted," is followed by 
eye and tube, the finger being held over the mouth 
of the latter, and at the critical moment the finger 
is removed, and the organism swept into the tube 
by the in-rushing water. Now wipe off the excess 
with a clean handkerchief, " spot " the organism in 
the tube again, and carefully absorb the super- 
fluous water with a piece of blotting paper ; and 
finally, gently but sharply blow the remainder on 
to the plate of the live-box, put on the cover, and 
examine with a one-inch power. If, as often 
happens, the organism sticks to the side of the 
tube, a little more water must be drawn in, and 
the process repeated. The use of the cotton-wool 
trap spoken of previously will often be very helpful 
in the examination of actively moving organisms. 

In the case of weeds, a small portion should be 
placed in the trough and carefully examined from 
end to end, first with the pocket lens and then 
with the one-inch power. Let us now consider 
the objects most likely to be met with. 



FRESHWATER SPONGE 135 

A piece of stick may be coated with a white 
layer, feeling rough to the touch, and full of small 
holes. The chances are that this will be a piece 
of freshwater sponge, Spongilla Jluviatilis, and by 
dark-field illumination particles may be seen to 
enter at some orifices and be ejected at others. 
"With a very high power and a very thin section, 
properly prepared, these holes will be seen to be 
the mouths of channels which are lined by the most 
delicate organisms possible, each having a minute 
body crowned with a tiny crystal cup, in the 
middle of which is a long cilium, or flagellum, as it 
is here called (Plate XIII. Fig. 1). The currents 
are produced by the combined action of these 
flagella. In point of fact, the sponge is a colony 
of minute animals working harmoniously for the 
common good. If the specimen be found in winter 
the sponge will be full of tiny balls, the "gem- 
mules " of the next season's growth. The roughness 
is due to the flinty spicules, which are at once the 
scaffolding and the protection of the sponge, and 
by boiling the sponge in a mixture of nitric acid 
and water (half and half) these spicules will be set 
free, and may be washed, allowed to settle, washed 
again, dried, and mounted in balsam. The gem- 
mules are coated by very beautiful spicules, con- 
sisting of two wheels connected by a rod. These 
may be treated in the same way. The life-history 
of the common sponge is as yet but imperfectly 
known. 

Perhaps the lowest form of life is the Amoeba, 
shown in Plate IX. Fig. 1, a mere lump of jelly, 



1 36 AM MA TED JELL Y 

which flows along, and when it comes into contact 
with any likely subject for digestion flows round 
it, encloses it, absorbs what it can from it, and 
leaves it behind. A near relative of the Amceba 
is the Arcella (Fig. 2), which is simply an Amoeba 
with a shell. Being unable to swim, these organisms 
are naturally to be most often found at the bottom 
of the collecting bottle, and it is always advisable 
to take up a portion of the debris with a dipping 
tube, which is then held upright on a slide with 
the finger upon it until the dirt settles on to the 
slide, when it is removed, a cover-glass put upon 
the dirt, and a quarter-inch power used for 
examination. Many forms will be discovered 
in this way which would otherwise escape 
observation. 

Another curious organism, of great size (com- 
paratively) and extreme beauty, is the sun animal- 
cule (AcUnophrys), which has a round body and 
long tentacles (Fig. 3), to which free-swimming 
organisms adhere, and by the combined action of 
the neighbouring ones are drawn to the body and 
received into it ; one cannot say swallowed. 

Fig. 6, Plate IX., shows the curious arithmet- 
ical process whereby the Infusoria multiply by 
division, a groove appearing at one point, rapidly 
deepening, and finally separating the animal com- 
pletely into two. The species is the CMlotlon, a 
flattened creature, ciliated all over, having a set of 
teeth arranged in the form of a tube, and at its 
fore-part a kind of membranous lip. A similar 
phenomenon, in an earlier stage, is shown in Fig. 



SPONGE ORGANISAfS 137 

26, Plate XI 11'., the organism in this case being 
Eupldtcs. 

It has been said that sponges are colonies of 
extremely minute organisms, each furnished with a 
membranous collar or funnel, the whole looking 
like an exquisite wine-glass without a foot. These 
organisms are not always grouped in colonies, how- 
ever. Many are free-growing, and may be found 
attached to the stems of water-plants, but they are 
extremely minute, and will hardly be noticed until 
the microscopist has acquired considerable ex- 
perience, nor even then — with such an instrument 
as we have postulated — will he see more than a 
tiny pear, with a straight line, the margin of the 
cup, on each side of its summit. The flagellum 
will be quite invisible. 

Some similar organisms may, nevertheless, be 
found which, though still minute, are within the 
range of a properly managed quarter-inch objective. 
Such an one, of extreme beauty, is the Dindbryon 
shown in Plate XIII. Fig. 3. Each "zooid," as 
the separate animals are called, among the Infusoria, 
or each generation of zooids, stands upon its parent 
and has two fiagella. When alarmed, the zooid 
sinks to the bottom of its cell, and withdraws its 
fiagella. In Fig. 2 (EugUna) we have a similar 
zooid, but of far greater size, and free -swimming. 
It is a very common object, and possesses a red 
eye-speck close to the "contractile vesicle." All 
Infusoria have the latter, some a great number, as 
in Fig. 9. The vesicle contracts at regular inter- 
vals, and is then simply blotted out, but reforms 



138 FLAGELLATED LNFUSORIA 

in the same place, so that it is probably the heart 
or the urinary bladder of these minute animals. 

The lovely rosette shown in Fig. 4 is the Synura, 
a spherical colony of zooids, each of which has 
two flagella, and is in addition clothed with rows 
of cilia. A beautiful sight it is to watch these 
colonies rolling through the field of view. Not 
uncommon, especially in brackish water, is the 
Peridinium (Fig. 5), with its plate armour, long 
flagellum, and girdle of cilia. A gigantic species 
of the same family is common in sea-water, and 
will be easily recognised by its body, not much 
larger than that of Peridinium, being furnished 
with three long arms, curiously bent. It is called 
Ceratium, and is sometimes present in such abund- 
ance as to thicken the water, near the surface of 
which it swims. 

We now come to a class of Infusoria which is 
characterised by the possession of a complete 
covering of cilia, arranged in rows all over the 
body. The number of these is enormous ; we can 
only glance at a few types, by mastering which the 
observer will, at all events, know whereabouts he 
is. The first we will take is the Coleps (Fig. 6), a 
very common kind, whose body is marked by a 
series of geometrical lines, so that the organism 
looks very much like an elongated geographical 
globe. These markings are on the tunic, which is 
of a brownish colour. Very different is the Trache- 
locerca (Fig. 7), with its long flexible neck, which 
is in constant movement from side to side as the 
creature swims along. As seen in the figure, the 



CILIATED FORMS 139 

neck is clear and the head lias a fringe of longer 
cilia. 

The Trachelitis (Fig. 8) is perhaps the largest of 
all the Infusoria, being readily visible to even an 
inexperienced eye. Its body is richly furnished 
with contractile vesicles, and the protoplasm is 
curiously reticulated. We may here remark that 
the Trachelius is especially prompt in doing what 
most of these organisms do when put under pressure 
in a live-box, namely, in performing a kind of hara- 
kiri. The outline first becomes irregular, then the 
body rapidly swells and finally comes to pieces, the 
fragments dancing mockingly away under the influ- 
ence of their still-moving cilia. The remedy is to 
use the cotton-wool trap and the lightest possible 
pressure. 

A very elegant organism is shown in the bottom 
right-hand corner of the Plate (Fig. 25). It is the 
Loxophyllum, and has a strongly marked contractile 
vesicle. 

Another large form is Ampliilcptus (Fig. 9), 
already referred to as having a large number of 
contractile vesicles arranged in a regular row ; 
and more massive still is Bxirmria (Fig. 10), a very 
curious organism, very much like a purse indeed, 
and possessing a wonderful arrangement of cilia 
inside the funnel. These are arranged like a ladder, 
a series of rows of short stiff cilia, which move at 
short intervals in unison, and tend to sweep down 
into the cavity any small particles of food. This 
arrangement is here described for the first time, 
and appears to be quite unlike anything else among 



j 4 o PARASITES 

the Infusoria. Not unlike Bursaria, but having no 
ladder, and being furnished with a delicate mem- 
branous pouch in front of the slit of the purse, is 
Condylostoma, which we shrewdly suspect to be the 
young form of Bursaria. This is a point which 
requires elucidation. 

One of the most beautiful of all these forms is 
shown in Fig. 1 1 , Folliculina, a type of a large 
group characterised by the possession of a trans- 
parent case, of extremely elegant form, within which 
the animal retreats on the slightest alarm. 

Fearless and independent, as becomes its size, is 
the trumpet-shaped Stentor (Fig. 12), which may 
easily be seen when present, as it is in almost 
every good gathering of water-weed. The par- 
ticular form drawn (S. Millleri) does not make a case, 
but many members of the genus do, and it is very 
common to see a stem almost covered with them. 
Such a sight, once seen under dark-field illumination, 
will never be forgotten. The method of multipli- 
cation of the Stentors (by division) is extremely 
easy to watch, and very instructive. 

A curious organism is TricJwdina (Fig. 13), which, 
though a free-swimmer, is always parasitic upon 
the body of some higher animal. We have found 
it sometimes upon Hydra, and always in hundreds 
upon the stickleback. The next group of Infusoria 
is distinguished by the body's being only ciliated at 
particular points, usually round the mouth, or what 
acts as such. The first form is Vorticella (Fig. 14), 
a beautiful vase-like creature upon a stem. Down 
the stem runs a muscular fibre, and on the least 




XIII. 



LIVING TREES 141 

shock the fibre contracts and draws the stem into 
a beautiful spiral, whilst the cilia are drawn in, 
and the zooid assumes the appearance of a ball at 
the end of a watch-spring. An exquisite sight is 
a colony of Vorticella?, for these actions are always 
going on, as, for example, when one member of the 
family touches another, which is quite sufficient to 
provoke the contraction. 

Many compound tree-like forms of Vorticella are 
known, one of which, Carchesium (Fig. 15), may 
serve as a type of all. In the case of this organism, 
the colony contracts in sections on a moderate 
shock ; in the second, Zoothamnium, as a whole ; 
whilst in Epistylis the stalks are rigid, and the 
individuals contract singly. When the shock is 
violent, the appearance presented by the two former 
is that shown in Fig. 16. In all three cases the 
colonies are usually so large that they are visible 
as trees to the naked eye, and some members of 
the group are extremely common. Moreover, they 
are often parasitic, as, for example, upon Cyclops, 
which is frequently loaded with them. 

Another compound form is Ophrydium, a colony 
of which (not unusually large) is shown of the 
natural size in Fig. 18, with a single zooid, magni- 
fied, by the side of it, in Fig. 19. 

Lastly, we have an exquisite group of organisms 
related to Vorticella, but possessing a transparent 
envelope, the forms of which are most varied, but 
always graceful. Vaginicola (Fig. 17) is a good 
example of this, and Cothurnia (Fig. 20) still 
more so. Many of these organisms, too, are fur- 



142 UNWELCOME GUESTS 

nished with a plate, attached either to the head or 
to the body, which plate, when they withdraw into 
their cases, closes the latter perfectly, as in the case 
of the exquisite Pyxicola (Fig. 21). 

A very interesting but singularly obtrusive 
organism is the Stylonychia (Figs. 22, 23). How 
often has it happened to us to have an interesting 
object nicely in the field of view, and then to have 
it knocked out of sight by the blundering incursion 
of this burly fellow, who runs so rapidly by means 
of his " styles " that he gives nothing time to get 
out of the way. He is of interest to us, however, 
as the representative of a class in which the body 
is not ciliated, or very partially and slightly so, 
usually round the mouth. We have frequently 
found Stylonychia, in company with Vorticella and 
Paramecium (Plate IX. Fig. 6), in the water in 
which flowers have been standing for a few days ; 
sometimes the numbers are so great as to make the 
water quite milky. 

One more form must conclude this short sketch 
of the great Infusorial family. It is the Acineta 
(Fig. 24), which, attached by its foot-stalk, and 
devoid of cilia, patiently waits, with outspread arms, 
to receive and embrace smaller members of the 
family as they dance merrily about. Alas ! its 
embrace is as fatal as that of the image of the 
Virgin which bore beneath its robe spikes and 
daggers, for the victim struggles vainly to escape, 
and the nourishment from its body is rapidly 
absorbed. 

And here we take our leave of a group which 



FURTHER INFORMATION 143 

simple as is the construction of the animals which 
it includes (for every one, great and small alike, is 
composed of a single cell), is yet full of beauty and 
interest. He who wishes to pursue the matter 
further will find in Saville Kent's Manual of the 
Infusoria a perfect mine of information, to which 
we gladly acknowledge our indebtedness, both now 
and in time past 



144 WORMS 



CHAPTER IX 

Fresh-water Worms — Planarians — Hydra — Polyzoa — Rotifers 
— Cheetonotus — Water-Bears. 

The fresh-water worms form a large and well- 
defined group, and a few words regarding them 
may be useful. 

They are very common, and very difficult to 
find information about, most of the work relating 
to them having been done in Germany. At the 
same time, they are so highly organised and so 
transparent that the process of their life-history 
may be easily followed. 

One large group has the peculiarity of multi- 
plying by division, the last joints or segments 
being devoted to the formation of the new in- 
dividual. At one time of the year the ordinary 
sexual process of reproduction takes the place of 
this method, and each worm is then surrounded by 
a belt such as may be seen in the common earth- 
worm under similar conditions. Further infor- 
mation on this subject is greatly needed. 

The type is the common Nais, which has a body 
of thirty segments or more, two eye-specks on the 
head, and a double row of bristles along the back ; 
whilst below, f-ach figment carries strong hooked 



TAILS AS LUNGS 145 

bristles, nearly buried in the body, by means of 
which the worm crawls. Inside the mouth is a 
large proboscis, which can be protruded, and this 
leads into a stomach which is merely an enlarge- 
ment of the intestine which succeeds it. The 
circulation of the blood (which is colourless) can 
be easily watched. It begins at the tail with a 
contraction of the dorsal vessel, passes up to the 
head, and then down below the intestine to the 
tail again. The intestine is ciliated inside, and it 
is by a current of water carried into the intestine 
by these cilia that the blood is aerated. 

In the next genus, Dero, this is clearly seen, for 
the tail (Plate XIV Fig. 1) is opened out into a 
wide shield, from which rise four, six, or even eight 
finger-like processes. These parts are all ciliated, 
and contain a network of blood-vessels. The worm 
lives in a case which it builds in the mud, and the 
way to find it is to put some of the mud into a 
glass beaker with water, and allow it to stand. 
If there be members of this family in it, their tails 
will be seen protruding above the water. Pour out 
the mud sharply, fill up with water, and allow the 
dirt to subside, and the worms may then be made 
to leave their cases by pressure by a camel hair 
pencil on the lower end of the tube, and may be 
caught with the dipping tube and placed in the 
live-box. They have no eyes, otherwise the general 
outline of the body closely resembles that of Nai's. 

Slavina (Fig. 2) has a row of touch-organs, like 
pimples, round each segment, and is a dirty looking 
creature, with an inordinately long first pair of 
10 



146 SPRING WORMS 

bristles, but this reaches its acme in Pristina (Fig. 
3) (sometimes, though wrongly, called Stylaria) 
parasita, which has three long sets of bristles upon 
the back, and keeps these in constant wing -like 
motion. The true Stylaria has a long trunk, set 
right in the head, and tubular (Fig. 6); it grows 
to a considerable length, and when in the stage of 
fission it is very funny to see the two proboscides 
waving about, one on the middle, as well as the 
original one at the head. There is also a form 
with a shorter proboscis of the same kind. 

JBohemilla has a tremendous array of saw-like 
bristles upon the back, whilst Chcdogastcr has none 
at all in this position, and few below. JEolosoma 
has merely tufts of hair instead of bristles, and 
swims freely. It is easily recognised by the red, 
yellow, or green pigment spots in its skin, and by 
the ciliated head. Earest of all the family is the 
one which connects it with the ordinary Tubifex, 
the red worm which lives in masses in the mud of 
brooks and ponds, the waving tails protruding above 
the water, and being instantly withdrawn when a 
foot is stamped upon the bank. Their Naid cousin 
is Naidium, and has red blood, but multiplies by 
fission, which Tubifex does not. 

Another group of worms is the Planarians, small 
leech-like worms, black, white, or brown, which are 
rarely absent from a gathering. The would-be 
investigator will find in them an abundant field for 
work, as they are but very imperfectly known or 
studied. 

The great enemy of all these worms is the 



POLYZOA 147 

Hydra, a good idea of which may be formed from 
Plate IX. Fig. 13. There are three species, all 
of which are fairly common. They capture their 
prey in exactly the same way as sea-anemones and 
the marine hydroid forms, so numerous and varied. 

Nor must we omit to notice the exquisitely beau- 
tiful Polyzoa, such as Zophopus (Plate XIV Fig. 4), 
with its ciliated tentacles and transparent social 
home ; Fredericella (Fig. 5), with its graceful stems, 
and their still more graceful inhabitants ; and the 
wonderful Crislatella, whose colonies form bodies 
which crawl over the stems of water plants. 
But for grace, beauty, and variety, the Eotifers 
assuredly outshine all their fellow inhabitants of 
our ponds and streams. 

"We can only take a few types, and of all these 
the most common is the common Eotifer (Plate IX. 
Fig. 10). It is there shown in the act of swim- 
ming, but it can withdraw its " wheels " and creep 
like a leech, protruding its foot as it does so. It is 
distinguished by the two eye-spots on the proboscis 
from PMlodina, in which they are on the breast, 
and Callidina, which has none. When at ease in 
its mind, the animal protrudes its wheels, and by 
their action draws in particles of food, these passing 
down to the incessantly moving jaws, which act 
like a mill and crush the food before it passes on to 
be digested. The movement of the jaws may even 
be seen in the young Eotifer whilst still in the egg 
within the body of the parent, and as the egg 
reaches its full development other eggs again 
are visible within it, so that we may have three 



143 MALE ROTIFERS 

generations in one individual. The males of most 
of the Kotifera are unknown. Those that are 
known are very lowly organised, having only the 
ciliary wreath and the reproductive organs, and 
are only found at certain seasons of the year. For 
the remainder of the time parthenogenesis is the 
rule, just as among the Aphides. We select a few 
individuals for illustration as types. Those who 
wish to pursue this study further must be referred 
to the monumental work of Hudson and Gosse. 

The common Eotifer, already referred to, may be 
taken as the type of the Bdelloida, or leech-like 
class, so called from their mode of " looping " them- 
selves along. The group is a comparatively small 
one in comparison with the next, the Ploima, or 
free-swimmers. "We can only select from the vast 
variety a few species, first of those classed as 
illoricated, from their being without a lorica, or 
case, and then of the loricated, which possess it. 
A very large and common form is Hydatina (Plate 
XIV Fig. 7), which lives by choice in the reddish 
pools of water found often by the roadside. It 
shows the whole organisation of the class magnifi- 
cently ; the ciliary wreath on the head, with the 
striped muscles which draw the latter back, the 
powerful jaws, the digestive canal with its crop and 
intestine, the ovary with the developing eggs, the 
water-vascular system with the curious vibratile 
tags, and finally, the cloaca, which receives the 
waste of the body and expels it at intervals. 

Another form, also common, especially in clear 
water, is Syncliccta (Fig. 8), very much like a kite 



MAILED ROTIFERS 149 

or peg-top in shape, which has the power of attach- 
ing itself by a glutinous thread, and spinning round 
at a tremendous rate. Then there is the gigantic 
Asjilanchna (Fig. 9), which has no opening below, 
so that the waste must be discharged by the mouth ; 
and curious Sacculus, which gorges itself with 
chlorophyll until it looks like a green bag with a 
string round it, but clear and sparkling. Of the 
Notommatm there is a whole host, but we can only 
mention the beautiful N. Aurita (Kg. 10), with an 
eye of a beautiful violet colour, composed of several 
spherules massed together, and two curious ear-like 
processes on the head, from which it takes its 
name. Some of the Ploima have powers of leaping 
which must be noticed. The Triarthra (Fig. 11) 
has three arms, or what we may call such, which 
it can stretch out suddenly and leap to a consider- 
able distance, whilst in Polyarthra the arms become 
a whole cluster of broad saw-like bristles. 

We pass on to note a few species of the mail- 
clad or loricated Eotifers, chief among which the 
great Euchlanis (Fig. 12), a noble-looking fellow, 
calls for our attention, his great size rendering him 
easily visible to the naked eye. It is difficult to 
avoid using the masculine gender, but, of course, all 
those figured and described are of the gentler sex. 
Salpina, too (Fig. 1 4), with its box-like lorica, armed 
with spines at each of the upper angles, and having 
three below, is quite easily recognised, and very 
common. JBrachionus (Fig. 13) has a shield-shaped 
case, well furnished with spines, symmetrically 
arranged at the top, and an opening below for the 



ISO A MARVELLOUS BUILDER 

flexible wrinkled tail, like the trunk of an elephant. 
Pterodina (Fig. 15) has a similar tail, but a round 
case, and the head is much more like that of the 
common Eotifer when extended. Anurcea (Fig. 16), 
on the other hand, has no tail, and its case is shaped 
like a butcher's tray, with a handle at each corner. 
Dinocharis (Fig. 17) has a roof -like case, with long 
spines on the root of the tail, and a forked stiff 
foot. Noteus (Fig. 18) is much like Pterodina, 
except in its foot, which more nearly resembles 
that of Dinocharis. 

The list might be indefinitely extended, but 
sufficient has probably been said to enable the tyro 
to find his bearings in this large, beautiful, and 
interesting class. 

"We pass on to notice in conclusion two or three 
of the fixed forms, of which a beautiful example is 
the Melicerta ringens (Plate IX. Fig. 7), whose build- 
ing operations have a never-ending charm. Par- 
ticles of debris are accumulated in a curious little 
cavity in the chin, in which they are whirled round, 
and mixed with a secretion which binds them 
together, and when a brick is made the head is 
bent down and the brick applied to the desired 
spot with mathematical regularity. By supplying 
fine particles of innocuous colouring matters, the 
Melicerta may be made to build a variegated case. 
The most remarkable specimen known is the one 
figured in Hudson and Gosse's work, which was 
found by the present writer in a specimen of water 
from which he had already obtained five-and-twenty 
species of various kinds of Eotifer ; the water was 



ON SA VING MA TERIA L 151 

collected by an inexperienced person, and there was 
only a pint of it. It had, moreover, been kept for 
three weeks, and the moral of that is, to preserve 
one's gatherings, and keep an aquarium into which 
they may be poured when done with for the 
moment. New forms will often develop with 
startling rapidity, their eggs having been present in 
the original gathering. The young form of Meli- 
certa, shown in Plate XIV Fig. 20, is strangely 
unlike its mother, and much more nearly resembles 
its father. 

Another group of extreme beauty is the Flos- 
cularite (Fig. 19), several species of which are very 
common. They will be easily known by their 
appearance, which resembles a shaving brush when 
closed ; whilst, when opening, the shaving brush 
resembles a cloud of delicate shimmering threads, 
which at last stand out straight, radiating all round 
the head of the creature, and forming the trap by 
means of which it catches its prey. Finally, there 
is the lovely Stephanoceros (not, unfortunately, very 
common), with its five symmetrically placed and 
gracefully curved arms, perhaps the most lovely of 
all Eotifers, with its exquisitely transparent body, 
sparkling with masses of green and golden brown. 
He who finds this has a treasure indeed, and will 
be encouraged to prosecute his studies in this 
" Fairyland of Microscopy." 

Two irregular forms call for a word of remark. 
The first is Chcetonotus (Plate XIII. Fig. 27), which 
stands on the borderland of the Infusoria and the 
Eotifers, neglected as a rule by the students of both ; 



152 WATER-BEARS 

and the second the Tar digr acta (Plate XIV Fig. 
21), or water-bears, which have feet like those of 
the red wriggling larva of Chironomns, whose silky 
tubes are common enough on submerged walls and 
on the stems of plants, these feet consisting of a 
mass of radially arranged hooklets, which can be 
protruded or withdrawn at will ; whilst the head of 
the water-bear is far more like that of a louse, 
pointed and hard, and suited for burrowing about, 
as the animal does, among the rubbish at the 
bottom of the bottle. Both the genera just re- 
ferred to will repay careful study, as little is 
known of their life-history or development. 

A few words must be devoted, in conclusion, to 
the Entomostraca, those shrimp-like animals which, 
like their marine relatives, act as scavengers to 
the community. Fig. 22 is a portrait of Cypris, a 
not very handsome form, but one very commonly 
found. Its shell is opaque, so that the internal 
organs are difficult to observe. Far different in 
this respect is the beautiful Daphnia, the water- 
flea par excellence, whose carapace is of crystalline 
clearness, so that every movement of every one 
of the internal organs may be followed with the 
greatest facility. There are many species of the 
genus, and some of them are very common, so that 
the opportunity of examining these lovely objects 
is easily obtained. Plate XIV. Fig. 23, shows the 
most common of all the class under notice, the 
Cyclops, so named from the fact that, like the fabled 
giants of classical literature, it has a single eye in 
the middle of its forehead. It is often loaded with 




E C Bn<t»fi'l i ad i it Ml 



XIV 



LAZY TIIIFVFS >f3 

Infusoria, especially Vorticclla and Epistylis, already 
described, to such an extent that its movements 
are greatly hampered. 

We have not space to figure more of these 
creatures, but other forms will be found not in- 
ferior in interest to those mentioned. The most 
curious of all are those which earn a dishonest and 
lazy living by attaching themselves to the bodies of 
other and larger animals, chiefly fish. One of the 
largest is the Argulus, the bane of aquarium 
keepers, which is of considerable size, and attacks 
gold-fish, and in fact almost any fish to which it 
can obtain access. 

The gills of the stickleback will furnish examples 
of the curious Ergasilus, which consists chiefly of 
an enormous pair of hooks and two long egg-bags, 
the latter, in varying form, being carried by many 
of the Entomostraca. 

Upon the fins of the same fish will be found the 
remarkable Gyrodactylus, a worm-like animal which 
attaches itself by a large umbrella-like foot, in the 
centre of which are two huge claws. The head is 
split down the middle for some distance. We may 
mention, in concluding our notice of the external 
and involuntary guests of the unlucky stickleback, 
that its skin is usually frequented by hosts of the 
Trichodina described in the last chapter. Of the 
internal parasites, want of space forbids us to 
speak. 



154 7 HE SEA 



CHAPTER X 

Marine Life— Sponges — Infusoria — Foraniinifera — Radiolaria 
— Hydroid Zoophytes — Polyzoa — -Worms — Lingual Rib- 
bons and Gills of Mollusca — Star-Fishes and Sea- Urchins 
— Cuttle- Fish —Corallines — Miscellaneous Objects. 

Great as is the range of objects presented to the 
student of fresh-water life, the latter field is limited 
indeed as compared with that afforded by the sea. 
The Infusoria and Eotifers furnished by the latter 
are, indeed, much fewer in number and variety, 
but the vast host of sponges, polyzoa, hydroids, 
Crustacea, molluscs, ascidians, and worms, to say 
nothing of the wealth of vegetable life, renders 
the sea the happy hunting-ground of the micro- 
scopist. 

Whether it be along the edge of the water, as 
the tide retreats, especially after a gale ; or in the 
rock-pools ; or, perhaps best of all, upon those 
portions of the shore left uncovered only by the 
lowest spring-tides, the harvest is simply inex- 
haustible. Stones turned up will exhibit a world 
in miniature. Encrusted with green or pink 
sponges, or with gelatinous masses of ascidians, 
fringed at its edges with hydroids, coated above 
with polyzoa, a single one will often supply more 



SPONGES AND THEIR SPICULES 155 

work than could be got through in a week (if 
steady application. 

A description of the fresh-water sponge already 
given may serve very well to indicate the general 
outlines of the organisation of the marine ones too. 
The spicules of the latter are, however, not always 
flinty; very often, as in the case of Grantia (Plate 
IX. Figs. 8 and 14), they are calcareous, a point 
which can be settled by the application of a little 
nitric acid and water. If lime be present there 
will be strong effervescence, and the separation of 
the spicules can only be effected by gently warm- 
ing a portion of the sponge in caustic potash 
solution, pouring the resulting mass into water, 
and allowing the spicules to settle. The washing 
and settling must be repeated several times, and a 
portion of the deposit may then be taken up with 
a dipping-tube, spread upon a slide and dried, and 
then covered in balsam solution. The forms are 
endless, and the same sponge will often supply 
three or four, or even more. Among them may 
be seen accurate likenesses of pins, needles, marlin- 
spikes, cucumbers, grappling -hooks, fish-hooks, 
porters'-hooks, calthrops, knife-rests, fish- spears, 
barbed arrows, spiked globes, war-clubs, boomerangs, 
life-preservers, and many other indescribable forms. 
The flinty forms must be prepared by boiling, as 
described in speaking of the mounting of diatoms 
in Chapter XL, except that, of course, only one 
settlement is required after thorough washing. 

Every one who has been by or on the sea on a 
fine summer night must have noticed the bright 



T5 fi A PIECE OF CHALK 

flashes of light that appear whenever its surface is 
disturbed ; the wake of a boat, for example, leaving 
a luminous track as far as the eye can reach. This 
phosphorescence is caused by many animals resident 
in the sea, but chiefly by the little creature repre- 
sented at Fig. 9, the NoctiHca, myriads of which 
may be found in a pail of water dipped at random 
from the glowing waves. A tooth of this creature 
more magnified is shown immediately above. 

A large group of microscopic organisms is known 
to zoologists under the name of Foraminifera, on 
account of the numerous holes in their beautiful 
shells, most of which are composed of carbonate 
of lime, though some are horny and others are 
composed of aggregations of minute grains of sand, 
the forms in one class often closely imitating those 
in another. It is of the shells of these minute 
animals that the " white cliffs of old England " are 
very largely composed, and those who desire to 
understand the part which these tiny creatures 
have played, and are playing, in geology, will do 
well to study Huxley's fascinating essay on "A 
Piece of Chalk." 

The inhabitants of these shells are Amoeba?, 
mere masses of jelly, and some forms may be 
found sliding over the weeds in almost every rock- 
pool. The anchor-mud, already spoken of, always 
contains some, and many forms may be found in 
the sand from sponges, which should be passed 
through a series of wire sieves, of increasing 
fineness, and the residuum in each case be ex- 
amined dry under a one-inch power. The shells 




XII. 



BEAUTY IN SAND 157 

may be picked up with a needle which has been 
slightly greased by being passed over the hair, and 
they may be mounted by sticking them to the 
slide with thin starch paste, putting on a cover- 
glass properly supported, and then running 
turpentine under the cover-glass, heating to expel 
the air, and finally filling up with balsam. Or, as 
opaque objects, they may be mounted in a cell 
dry. The forms are endless, but all are beautiful, 
and a few examples are given in Kate IX. Fig. 4 
{MilioUna), and Plate XII. Fig. 7, which is a 
portion of the shell to show the holes, Fig. 13 
{Polystomella), Fig. 14 (Truncatulina), Fig. 15 
(PolymorpMna), Fig. 1 6 {MilioUna, partly fossilised), 
Fig. 18 (LagSna), and Fig. 20 {Biloculina). 

Allied to these are the lovely Kadiolaria, whose 
shells, constructed on a similar plan, are composed 
of flint. They are found in remarkable profusion 
in the deposit from Cambridge, Barbados, but also 
in a living state at even enormous depths in the 
ocean. The present writer has obtained many 
forms from Challenger soundings, and the great 
authority on this subject is Haeckel's report in the 
official accounts of the expedition of the above- 
named vessel. 

The Hydroid Zoophytes are represented by 
several examples. These creatures are soft and 
almost gelatinous, and are furnished with tentacles 
or lobes by which they can catch and retain their 
prey. In order to support their tender structure 
they are endowed with a horny skeleton, sometimes 
outside and sometimes inside them, which is called 



iS8 JELLY-FISH 

the polypidom. They are very common on our 
coasts, where they may be found thrown on the 
shore, or may be dredged up from the deeper 
portions of the sea. 

Fig. 13 is a portion of one of the commonest 
genera, Sertularia, showing one of the inhabitants 
projecting its tentacles from its domicile. Fig. 15 
is the same species, given to show the egg-cells. 
This, as well as other zoophytes, is generally classed 
among the sea-weeds in the shops that throng all 
watering-places. 

The form just referred to is a near relative of 
the Hydra, already described, and belongs to the 
same great family as the sea-anemones. One form, 
shown in Fig. 26, is the Hydra Tuba, long thought 
to be a distinct animal, but now known to be the 
young form of a jelly-fish, or Medusa. The Hydra 
Tuba throws off joints at intervals, each of which 
becomes a perfect jelly-fish. One of them is shown 
in Fig. 27. Fig. 28 represents a very small and 
pretty Medusa, the Thaumantias. When this 
animal is touched or startled, each of the purple 
globules round the edge flashes into light, producing 
a most beautiful and singular appearance. Fig. 29 
exhibits the so-called compound eye of another 
species of Medusa, though it would appear that 
these are really connected with the nervous system 
of the animal, and have to do with the pulsating 
contractions of the bell by which it is propelled 
through the water. 

In my Common Objects of the Sea-Shore the 
Actiniae, or Sea- Anemones, are treated of at somo 



MARINE POLYZOA 159 

length. At Fig. 1G is shown part of a tentacle 
flinging out the poison-darts by which it secures 
its prey , and Fig. 1 7 is a more magnified view of 
one of these darts and its case. 

Much more might be said under this head, but 
we must pass on to another group, which, whilst 
possessing a certain general resemblance to the 
hydroid zoophytes, differs utterly from them in 
internal organisation. We have already referred 
to the fresh-water polyzoa. The marine forms are 
vastly more numerous, and more easily found, since 
not only pieces of weed upon which they grow 
are to be found upon every beach, but whole 
masses of leaf-like colonies, forming what is known 
as horn- wrack, may be plentifully found. Instead 
of the tentacles armed with sting-cells, like the 
anemone's, possessed by the Hydrozoa, the Polyzoa 
have arms clothed with active cilia, by which the 
food is swept into the mouth, passing on into the 
stomach, and then through the intestine to another 
opening. 

Fig. 19 is a very curious zoophyte called 
Anguinaria, or snake-head, on account of its 
shape, the end of the polypidom resembling the 
head of the snake, and the tentacles looking like 
its tongue as they are thrust forward and rapidly 
withdrawn. Fig. 21 is the same creature on an 
enlarged scale, and just below is one of its 
tentacles still more magnified. Fig. 23 is the 
ladies'-slipper zoophyte (Eretea); and Fig. 24 is 
called the tobacco-pipe or shepherd's-purse zoo- 
phyte {Notamia). 



160 MARINE WORM}s 

Fig. 22 is a portion of the Bugula, with one of 
the curious " birds'-head " processes. These ap- 
pendages have the most absurd likeness to a bird's 
head, the beak opening and shutting with a smart 
snap (so smart, indeed, that the ear instinctively 
tries to catch the sound), and the head nodding 
backward and forward just as if the bird were 
pecking up its food. On Plate XII. Fig. 2, is a 
pretty zoophyte called Gemellaria, on account of 
the double or twin-like form of the cells ; and 
Fig. 5 represents the Antennularia, so called on 
account of its resemblance to the antenna? of an 
insect. Fig. 22 is an example of a pretty zoophyte 
found parasitic on many sea-weeds, and known by 
the name of Membranipora. Two more specimens 
of zoophytes may be seen on Plate XII. as they 
appear under polarised light. Fig. 17 is the 
Gellularia reptans ; and Fig. 20 is the Bower- 
banhia, one form of which occurs in fresh water. 

Among the worms we may refer to the beautiful 
little Spirorbis, whose tiny coiled spiral tube may 
be found attached to almost every sea-weed, and 
which, when placed in a trough of sea-water, 
protrudes its beautiful crown of plumes. In chalk 
or other soft rocks, again, the tubes of Spio, with 
its two long waving tentacles, may be found by 
hundreds. Then there are the centipede -like 
worms, which may be found under nearly every 
stone, and which belong to the great family of 
Nereids, provided with formidable jaws and stiff 
bristles of various forms. The Serpuloe are allied 
to the Spirorbis already mentioned. Parts of the 



TRANSFORMATION SCENES 161 

so-called feet of one of these worms are shown in 
Fig. 36, where the spears or "pushing-poles" are 
seen gathered into bundles, as during life. One 
of them, on a larger scale, is shown in Fig. 32. 
The gorgeous hairs of Aphrodite have already been 
alluded to. 

In the sea the few species of Crustacea which 
fresh water offers to the observer in the shape of 
Cyclops and its allies become thousands, and their 
changes during development are numerous and 
puzzling. Who, for example, would suppose that 
the young stage of the Cyclops was indistinguish- 
able in habits, and almost in form, from that of 
the barnacle which adheres to the rocks ? Yet 
such is the case, and there are other metamor- 
phoses even more startling. Fig. 25 is the larva 
of the common crab, once thought to be a separate 
species, and described as such under the name of 
Zocea. 

The Mollusca proper will not afford us many 
objects, except in the form of their lingual ribbon, 
which may be extracted from the mouth, gently 
heated in liquor potassce, and mounted in balsam 
after well washing, when the rows of teeth form 
splendid objects by polarised light. The palate of 
a whelk is shown in Plate XI. Fig. 19. 

Again, the gills of the mussel will afford a 
beautiful illustration of ciliary action. If a por- 
tion of the thin plates which lie along the edge 
of the shell be examined in a little of the liquor, 
the action may be splendidly seen, and watched for 
a long time (Fig. 39). 
ii 



i62 FICTION AND FACT 

The structure of shell, e.g. oyster-shell, is well 
shown in three examples: Fig. 34 is a group of 
artificial crystals of carbonate of lime ; and on 
Figs. 38 and 39 may be seen part of an oyster- 
shell, showing how it is composed of similar 
crystals aggregated together. Their appearance 
under polarised light may be seen on Plate XI. 
Figs. 1 and 6. 

"We now pass on to the Echinoderms, including 
the star-fishes and sea-urchins. 

The old story of the goose-bearing tree is an 
example of how truth may be stranger than fiction. 
For if the fable had said that the mother goose 
laid eggs which grew into trees, budded and 
flowered, and then produced new geese, it would 
not have been one whit a stranger tale than the 
truth. Plate IX. Fig. 33, shows the young state 
of one of the common star-fishes (Comdtula), 
which in its early days is like a plant with a 
stalk, but afterwards breaks loose and becomes 
the wandering sea-star which we all know so well. 
In this process there is just the reverse of that 
which characterises the barnacles and sponges, 
where the young are at first free and then become 
fixed for the remainder of their lives. Fig. 30 is 
the young of another kind of star-fish, the long- 
armed Ophiuris, or snake-star. 

Fig. 37 is a portion of the skin of the common 
sun-star (Solaster), showing the single large spine 
surrounded by a circle of smaller spines, supposed 
to be organs of touch, together with two or three 
of the curious appendages called pedicellarise. 



SEAUKCHINS 163 

These are found on star-fishes and Echini, and 
bear a close resemblance in many respects to the 
bird-head appendages of the zoophytes. They are 
fixed on foot-stalks, some very long and others 
very short, and have jaws which open and shut 
regularly. Their use is doubtful, unless it be to 
act as police, and by their continual movements to 
prevent the spores of algae, or the young of various 
marine animals, from effecting a lodgment on the 
skin. A group of pedicellariee from a star-fish is 
shown on a large scale on Plate XII. Fig. 6, and 
Fig. 9 of the same Plate shows the pedicellarios of 
the Echinus. 

Upon the exterior of the Echini, or sea-urchins, 
are a vast number of spines having a very beautiful 
structure, as may be seen by Fig. 35, Plate IX., 
which is part of a transverse section of one of 
these spines. An entire spine is shown on Plate 
XII. Fig. 12, and shows the ball-and-socket joint 
on which it moves, and the membranous muscle 
that moves it. Fig. 8 is the disc of the snake-star 
as seen from below. Fig. 1 is a portion of skin 
of the sun-star, to show one of the curious 
madrepore-like tubercles which are found upon 
this common star-fish. Fig. 3 is a portion of 
cuttle " bone," very slightly magnified, in order 
to show the beautiful pillar-like form of its 
structure ; and Fig. 4 is the same object seen 
from above. When ground very thin this is a 
magnificent object for the polariscope. 

One or two miscellaneous objects now come 
before our notice. Fig. 1 1 is one of those curious 



1 64 INJECTIONS 

marine plants, the Corallines, which are remarkable 
for depositing a large amount of chalky matter 
among their tissues, so as to leave a complete 
cast in white chalk when the coloured living 
portion of the plant dies. The species of this 
example is Jania rubens. 

Fig. 19 is part of the pouch-like inflation of the 
skin, and the hairs found upon the rat's tail, 
which is a curious object as bearing so close a 
similitude to Fig. 22, the sea-mat zoophyte. 
Fig. 23 is a portion of the skin taken from the 
finger, which has been injected with a coloured 
preparation in order to show the manner in which 
the minute blood-vessels or " capillaries " are dis- 
tributed ; and Fig. 26 is a portion of a frog's lung, 
also injected. 

The process of injection is a rather difficult one, 
and requires considerable anatomical knowledge. 
The principle is simple enough, being merely to fill 
the blood-vessels with a coloured substance, so as 
to exhibit their form as they appear while distended 
with blood during the life of the animal. It some- 
times happens that when an animal is killed 
suddenly without effusion of blood, as is often seen 
in the case of a mouse caught in a spring trap, 
the minute vessels of the lungs and other organs 
become so rilled with coagulated blood as to form 
what is called a natural injection, ready for the 
microscope. 

Before leaving the subject I must ask the reader 
to refer again for a moment to the frog's foot on 
Plate X., and to notice the arrangement of the dark 



riCMENT-CELl S 165 

pigment spots. It is well kimwn that when frogs 
live in a clear sandy pond, well exposed to the rays 
of the sun, their skins are bright yellow, and that 
when their residence is in a shady locality, especially 
if sheltered by heavy overhanging banks, they are 
of a deep blackish-brown colour. Moreover, under 
the influence of fear they will often change colour 
instantaneously. The cause of this curious fact is 
explained by the microscope. 

Under the effects of sunlight the pigment granules 
are gathered together into small rounded spots, as 
seen on the left hand of the figure, leaving the skin 
of its own bright yellow hue. In the shade the 
pigment granules spread themselves so as to cover 
almost the entire skin and to produce the dark 
brown colour. In the intermediate state they 
assume the bold stellate form in which they are 
shown on the right hand of the round spots. Very 
remarkable forms of these cells may be found in 
the skin of the cuttle-fish. 

Figs. 24 and 25 are two examples of coal, the 
former being a longitudinal and the latter a trans- 
verse section, given in order to show its woody 
character. Fig. 17 is a specimen of gold-dust 
intermixed with crystals of quartz sand, brought 
from Australia ; and Fig. 2 1 is a small piece of 
copper-ore. 

Every possessor of a microscope should, as soon 
as he can afford it, add to his instrument the 
beautiful apparatus for polarising light. The 
optical explanation of this phenomenon is far too 
abstruse for these pages, but the practical application 



1 66 POI.AKISCOFY 

of the apparatus is very simple. It consists of two 
prisms, one of which, called the polariser, is fastened 
by a catch just below the stage ; and the other, 
called an analyser, is placed above the eye-piece. 
In order to aid those bodies whose polarising 
powers are but weak, a thin plate of selenite is 
generally placed on the stage immediately below 
the object. The colours exhibited by this instru- 
ment are gorgeous in the extreme, as may be seen 
by Plate XI., which affords a most feeble repre- 
sentation of the glowing tints exhibited by the 
objects there depicted. The value of the polariser 
is very great, as it often enables observers to dis- 
tinguish, by means of their different polarising 
properties, one class of objects from another. 

If the expense of a polarising apparatus be too 
great for the means of the microscopist, he may 
manufacture a substitute for it by taking several 
thin plates of glass, arranging them in a paper tube 
so that the light may meet the surface of the 
lowest one at an angle of about 52°, and placing 
the bundle above the eye-piece to act as an analyser; 
whilst, by using a plate of glass, and so arranging 
the lamp that the light falls upon it at the above 
angle, and is reflected up the tube of the micro- 
scope, he will find on rotating the extemporised 
analyser that the phenomena of polarisation are to 
a great extent reproduced; whilst by splitting an 
extremely thin film from the surface of a sheet of 
mica, such as is employed for making smoke-screens 
above glass globes, he will have a substitute for the 
selenite by means of which alone can the gorgeous 




XL 



CHEAP APPARATUS 167 

colour effects be produced. The extemporised 
apparatus will not, of course, give such perfect 
effects, but this is sometimes an advantage, and 
the present writer has used the same means with 
considerable success in photographing starch - 
granules. 



1 68 MOUNTING 



CHAPTER XI 

Hints on the Preparation of Objects — Preservative Fluids- 
Mounting Media — Treatment of Special Objects. 

The microscopist who relies altogether on the dealer 
for his permanent preparations may expend a good 
deal of money, but the satisfaction which he derives 
from his hobby will be very inferior to that ex- 
perienced by the worker who endeavours to secure, 
for exhibition or for reference, specimens of the 
objects which he finds most interesting and instruct- 
ive to himself. 

It will be our endeavour in the following pages 
to give a summary of the elementary principles 
upon which reliance is to be placed, though it 
must be clearly understood that the technique of 
the subject, already occupying a vast amount of 
literature, is extending day by day, so that it is 
impossible to deal exhaustively even with one 
single section of it. Reference must be made, for 
further information, to such publications as the 
Journal of the Royal Microscopical Society, or that of 
the Quekett Club, or to the monographs on the 
various departments. Davies' work on the general 
subject will also be found useful by the beginner. 

Taking first the question of reagents, we may 



PA' FSF.R T 'A TI J 'F.S 1 69 

mention five which leave the cells of a tissue as 
nearly as possible in the natural condition, but fit 
for permanent preservation. The first of these, in 
order of importance and of general applicability, is 
alcohol, represented for most purposes by methy- 
lated spirit, which contains about 84 per cent, of 
absolute alcohol, though, unfortunately for our pur- 
pose, there is a certain quantity of mineral naphtha 
in it in addition. This last has the effect of making 
it go milky upon dilution with water, which is a 
considerable disadvantage, though the milkiness 
disappears to some extent on standing, and it is 
rarely worth the while of the ordinary microscopist 
to go through the formalities necessary to obtain 
permission to purchase unmineralised spirit, which 
cannot be had in quantities of less than five gallons 
(as it is only to be had from the distillers under an 
Excise permit), and distillers may not supply less. 

Four parts of methylated spirit with one of 
water forms the classical "70 per cent. " alcohol, 
the most generally useful of all fluids for hardening 
and preserving purposes. A considerable quantity 
of this fluid should always be available. 

Whatever other fluid may be used to begin with, 
spirit must almost always be used to finish the 
process, and fit the tissue for section-cutting and 
Btaining. 

Of purely preservative, or fixative, fluids, we 
may mention "formalin," a 40 per cent, solution 
of formic aldehyde, which is rapidly coming to the 
front, as indeed it deserves to do. It is but slightly 
poisonous, if at all, and leaves in the tissue nothing 



i;o MOUNTING MEDIA 

which requires subsequent removal before proceed- 
ing to harden for section-work, whilst it is an 
admirable preservative of cell-form. 

Another admirable but highly poisonous reagent 
is corrosive sublimate, in saturated solution, with 
2 per cent, of acetic acid. 

A fourth is osmic acid, used in 1 per cent, 
solution. This is a highly valuable reagent, but 
extremely expensive, very poisonous, and giving off 
fumes which are most irritating to the eyes. 

The fifth, a very gentle, but in many respects 
very satisfactory one, is picric acid in saturated 
solution. Tissues preserved in this medium must 
not be washed out with water, as it enters into 
very feeble combination with protoplasm, and the 
cells swell and disintegrate as the reagent is dis- 
solved out. 

Of mounting media we may mention glycerine, 
glycerine jelly (made by dissolving starch in gly- 
cerine with the aid of heat), and Canada balsam, 
dissolved in xylol or benzole. The Canada balsam 
must be dried hard by evaporation over a water- 
bath, and dissolved as wanted. Under no circum- 
stances should raw balsam be used, as it takes 
years to set hard, and turns of a deep yellow colour 
in the process. 

Chloroform is frequently used as a solvent, but 
it has the disadvantage of attacking and extracting 
a large number of the aniline dyes used for staining 
structures, an objection from which the mineral 
solvents are free. 

We will now proceed to go through the objects 



HOW TO PROCEED 171 

already referred to, and indicate the method <>f 
preservation. 

For the study of the cell-structures of plants the 
portion to be examined is to be placed in spirit of 
about 30 per cent, strength, which is changed after 
twenty-four hours for 40 per cent., after a further 
twenty-four hours for 55 per cent., and finally, as 
regards our present purpose, in 70 per cent, spirit, 
in which it may remain until required for section- 
cutting. The effect of this treatment is to extract 
the bulk of the water from the tissue, with the 
minimum of shrinkage of the cells, the latter being 
preserved in their natural relations to surrounding 
parts. 

In some cases, however, it is desirable to examine 
and preserve delicate structures, or parts, or dis- 
sections, in a medium which allows of the retention 
of the greater part of the natural moisture, and in 
such a case the tissue is immersed in glycerine 
diluted very much in the same way as the alcohol 
in the last process, but with very much longer 
intervals between the alterations of strength, until 
it reaches pure glycerine, in which it remains for a 
considerable time, as the exchange between the 
tissue and the dense fluid surrounding it goes on 
very slowly. 

A combination of the two methods is also possible, 
the spirit-hardening being carried out for a portion 
of the time, and the tissue being thereafter trans- 
ferred to glycerine, diluted or pure. 

The object of using glycerine at all is merely 
that it has a much lower refractive index than 



172 MOUNTING STARCH 

balsam, so that delicate structures may sometimes 
be better seen in the former medium, but balsam 
is to be preferred wherever it is possible to use it, 
i.e. almost always. The writer has not mounted a 
preparation in glycerine or a medium containing it 
for many years, nor, with proper staining, does he 
think it can ever be necessary to do so, except in 
the case of dissections in which the glycerine can 
be slowly run in without disturbing the arrange- 
ment, as spirit would be pretty sure to do. The 
harder portions of plants, woody stems, shells of 
fruit, or the like, require different treatment, and 
must, as a rule, be allowed to dry thoroughly before 
being cut. 

Starch granules are somewhat troublesome to 
mount satisfactorily. The writer has tried many 
methods, and, on the whole, prefers a glycerin- 
gelatin medium, which keeps for an almost in- 
definite time, and may be made as follows : Thirty 
grains of gelatine (Nelson's " brilliant " or other 
transparent gelatine is to be preferred) are allowed 
to soak in water, and the swollen gelatine is 
drained, and dissolved in the water which it has 
absorbed, by the aid of a gentle heat. An equal 
bulk of pure glycerine is then added. In using, a 
small portion is transferred to a slide with the 
point of a knife and melted, a small quantity of 
starch granules added, and stirred into it with a 
needle. The cover-glass is then laid up on the still- 
fluid drop, pressed gently down so that the drop is 
extended to the margin of the cover, and the whole 
allowed to cool. It is then to be painted round with 



MOUNTING DRY 173 

several layers of Brunswick black, or Hollis's glue, or 
zinc-white cement, to prevent evaporation, — Hollis's 
glue being perhaps the best medium for the purpose. 

Petals, or other parts of which it is desired to 
obtain a surface view, must be mounted in cells, 
which may be made by the use of button-moulds 
of suitable size, cemented to the glass slide with 
marine glue. The slide must be free from grease, 
as the tissue must be fixed in position by the use 
of gum, and allowed to dry thoroughly before closing 
the cell, or the cover-glass will be bedewed with 
moisture when the cell is closed. The best plan is, 
after air-drying for a couple of days, to place the 
preparation on a metal plate over a beaker of boil- 
ing water for an hour or more, and then to close 
the cell immediately with Brunswick black, main- 
taining the heat at first to ensure rapid drying, and 
then slowly withdrawing it. When cool, another 
coat should be given, and rather thick covers should 
be used, as these preparations are never required to 
be examined with high powers. 

To mount pollen-grains, they should be sprinkled 
upon the surface of a slide which has been pre- 
viously moistened with thin gum, and allowed to 
dry until it has become just " tacky " ; the drying 
is then completed by gentle heat and a drop of 
balsam placed upon the grains, with a cover-glass 
over all. Bubbles will probably form, but with 
Canada balsam this is not of the slightest import- 
ance, as they always come out of their own accord, 
and balsam mounts should never be closed with 
cement of any kind until thoroughly dry. 



174 



AIR-BUBBLES 



Air-bubbles in other media may be eliminated 
by the use of the air-pump shown in Fig. 16, 
which may be obtained from Baker at a very 
reasonable rate, and which is nseful not only for 
that purpose, but for accelerating the drying of 
moist tissues. To do this, there is placed upon the 
plate of the pump a porcelain dish containing 
strong sulphuric acid, and upon this is placed a 
little triangle of platinum wire, which serves to 
support the preparation. The air is now ex- 
hausted; the tissue 
parts with mois- 
ture to supply its 
place, and this 
moisture is in turn 
ereedilv absorbed 
by the sulphuric 
acid, so that dry- 
ing is rapid and 
continuous, as well 
as very thorough, 
whilst the process has the great advantage of dis- 
pensing entirely with the use of heat. 

Portions of many of the delicate algse may be 
mounted in glycerine, having previously been soaked 
in it as already described ; whilst the unicellular 
forms, such as desmids and diatoms, may be pre- 
served in almost exactly the natural condition by 
simply mounting them in a saturated solution of 
picric acid. 

Probably formalin, in a solution of 10 per cent, 
strength, would answer the purpose equally well, 




Fn;. 16. 



DIATOMS 175 

but the writer has not tried it. It is hardly 
necessary to say that, with such extremely fluid 
media, great care is required in closing the cell. 
A thin layer of Hollis s glue should be first painted 
on, to secure the cover in position, and when this 
is thoroughly dry, several successive layers must 
be added in the same way 

It may be said here, that it is advisable in all 
cases to use circular cover-glasses, as far as possible, 
as they lend themselves with great facility to a 
mechanically accurate closure. This slide is placed 
upon a turn-table, carefully adjusted until the cover 
is seen to be central when rotated, and a brush, 
preferably a small camel-hair pencil, charged with 
the desired fluid, but not in large excess, is held 
against the junction of the slide and cover, whilst 
the table is rapidly spun. A little experience will 
teach better than any description what amount of 
fluid there should be in the brush, and how thick 
the cement should be. If too thick, it will drag off 
the cover ; if too thin, it will flow over the latter 
and over the slide. 

The preparation of diatom -skeletons as per- 
manent objects is easy. Consisting, as they do, 
of pure silex, or flint, — i.e., practically glass, — they 
resist long boiling in acids, so that there is little 
difficulty in isolating them from any organic matter 
with which they are mingled. It is generally 
recommended to treat them with strong nitric 
acid. This is a mistake. The acid acts much 
more powerfully and less violently when diluted 
witli an equal bulk of water, and it is in an acid so 



1 76 SEDIMENT A TION 

diluted that portions of water-plants, or other 
diatomaceous material, should be boiled in a glass 
beaker until all the organic matter is dissolved. 
The beaker should be covered with a glass plate, 
to prevent dissipation of the acid fumes. When 
the process is complete, usually in about half an 
hour, the contents of the beaker are thoroughly 
stirred with a glass rod, poured rapidly off into a 
larger bulk of cold water, and allowed to settle for 
another half-hour. The process is then repeated 
with a smaller bulk of water, several times, to 
allow the removal of the last traces of acid, and 
finally with distilled water. The separation of the 
diatoms into grades is effected by settlement. The 
final result is poured into a tall glass vessel, and 
allowed to settle for, at first, a minute, the super- 
natant fluid again poured off, and allowed to settle 
for two minutes, and so on, the period being gradu- 
ally increased, and each sediment preserved apart. 
The first will probably only be sand, but the propor- 
tion of diatoms will increase with each separation, 
though there will always be a certain proportion of 
sand of such a size as to settle at the same rate 
as the diatoms. Marine plants especially will 
furnish a rich harvest by treatment as described. 

Solid diatomaceous deposits, such as kiesel-guhr, 
mountain-meal, and especially the famous Oamaru 
deposit from New Zealand, demand different treat- 
ment, and perhaps the best way is to disintegrate 
the mas^s, either by boiling with Sunlight soap 
(though the alkali attacks the flint to some extent) 
or to mix the mass with a super-saturated solution of 



SELECTING DIATOMS 177 

acetate of soda (made by saturating water with the 
crystals whilst boiling), and by successive coolings, 
heatings, and stirrings to cause the process of 
crystallisation to break up the mass, which it 
will do very thoroughly. The diatoms are then 
separated by sedimentation, as above described. 

A small portion of the deposit may now be 
spread thinly on a glass slide, allowed to dry 
thoroughly, be treated with balsam, and covered. 

If it be desired to select individual diatoms, 
this must be done under the microscope, by means 
of a bristle fixed in a handle either with glue or 
sealing-wax. The diatom selected will adhere to 
the bristle if the latter be slightly greasy, and 
should then be transferred to a slightly adhesive 
slide, coated either with thin solution of white 
shellac, or with thin gum nearly dry. When the 
forms desired are mounted, the preparation should 
be covered in balsam. The process is by no means 
as easily effected as described, however. 

The preparation of insects, or parts of insects, as 
microscopic objects is a tedious and difficult task. 
The main point is the trouble of softening the 
integument and eliminating the colour. 

The latter can, in any case, be only partially 
effected. The beginner would do well to begin 
with a fairly easy form, such as the worker-ant. 
A good supply of these insects may be placed in a 
bottle of liquor potassse, and left there for at least 
some days until they begin to become clear and 
limp. From time to time a specimen may be 
taken, well washed with several waters, then with 



178 MOUNTING INSECTS 

acetic acid and water of a strength of about 10 
per cent., then with weak spirit, about 50 per cent. 
An attempt may then be made to arrange the 
insect upon a slide, spreading out the legs so as 
to exhibit them to the best advantage, and when 
this has been done a cover-glass may be put on, 
supported in such a way as to prevent absolute 
pressure. The spirit is then withdrawn by means 
of a piece of filtering-paper cut to a point, and 
strong spirit added. This is again succeeded by 
absolute alcohol, then by a mixture of turpentine 
and crystal carbolic acid in equal proportions, and 
finally the cover-glass is carefully lifted, and some 
thick balsam solution dropped on, the limbs finally 
arranged by means of warm needles, and the cover- 
glass carefully replaced and pressed gently down 
by means of a clip, which may be obtained for a 
few pence. The whole is then set aside to harden, 
the deficiency caused by evaporation made good, 
the balsam allowed to dry, and the preparation 
finally painted round. 

The contents of the body, in large insects, must 
be removed, and this is effected during the washing 
in water by gentle pressure with a camel-hair 
brush, the process being aided, if necessary, by a 
small incision made through the integument at the 
root of the tail. Sections of insects require very 
special methods, which will hardly fall within the 
scope of tfris work. 



IMBEDDING H9 



CHAPTER XII 

Section-Cutting — Staining 

No method of examination can equal, for general 
applicability and usefulness, that of section-work. 
The relations of the parts to each other being 
preserved, it is possible to draw conclusions as to 
their actual relations which no other mode allows 
of, and we shall devote this concluding chapter to 
some account of the methods to be employed to 
tins end. 

The apparatus required is not necessarily com- 
plicated. Keduced to its elements, it consists 
essentially only of a razor to cut the sections and 
a dish to receive them. It but seldom happens, 
however, that the relations of the parts in suffi- 
ciently thin sections can be preserved by such a 
rough-and-ready method, and frequently the object 
to be cut is of such small dimensions as to render 
it impossible to deal with it in this way. It is 
therefore necessary to " imbed " it, so as to obtain 
a handle by which to hold it, in such a way that 
it shall be equally supported in all directions. 
Moreover, since the human hand can only in ex«- 
ceptional cases be brought to such a pitch of skill 



i So FREEZING TISSUES 

as bo cut a series of sections, or even single ones, 
of the needful delicacy, some mechanical means 
of raising the object through a definite distance 
is highly desirable. The writer has cut many 
thousands of sections with the " free hand," but 
the personal equation is a large one,- and is not 
always the same in the same person. For single 
sections the method will, with practice, succeed 
very well, but some means of securing a number 
of sections of more or less the same thickness is 
usually required. 

Let us deal with the imbedding first. 

If it be desired to imbed a tissue which has 
merely been fixed with formalin, the block should 
be immersed in strong gum (made by saturating 
water with picked gum arabic, white and clean) 
for several days. It is then taken out and, with- 
out draining, transferred to the plate of a freezing 
microtome, and the sections cut from the frozen 
block, and mounted in glycerine at once. 

This plan is of limited usefulness, since it allows 
of very little differentiation of the tissue elements, 
and that only optical. 

To get the best results, some plan of staining 
must be adopted. Perhaps the simplest, and cer- 
tainly a very excellent one, is as follows. After 
the tissue has been passed from the hardening, or 
fixing, fluid into the successive alcohols, as described, 
it is placed in the following solution. Take about 
forty grains of carmine and eighty grains of borax, 
dissolve in about an ounce of water, add to the 
mixture an ounce of methylated spirit, and let it 



STAINING AND CUTTING 181 

stand for some time with frequent shaking ; about 
a week will be sufficient, and the process of solution 
may be hastened by gentle warming at intervals. 
The clear upper portion is then poured off, and 
into this the block of tissue is dropped, and allowed 
to remain until thoroughly penetrated. Perhaps 
the best plan is to substitute the carmine solution 
for the 50 per cent, alcohol, and thus to make the 
staining a stage in the hardening process. From 
the carmine solution the tissue is transferred to 
70 per cent, alcohol, to each ounce of which two 
drops of hydrochloric acid have been added, and 
after remaining in it for a day (with a piece of 
the usual size) is placed in 70 per cent, alcohol, 
in two successive quantities. Sections from this 
material now only require treatment with the car- 
bolic acid and turpentine above mentioned to be 
fit for mounting and covering in balsam. We now 
proceed to indicate how the sections may be cut. 

A mixture of wax and almond oil, in proportions 
varying with the heat of the weather, usually about 
equal ones, is prepared. The piece of tissue is freed 
from superfluous spirit by being placed on a bit of 
blotting-paper for a minute or two, and is then 
immersed in a quantity of the wax-aud-oil mixture 
contained in a little box of paper or lead-foil. The 
tissue is held on the point of a needle, and lifted 
up and down until it is coated with the mixture, 
and, before solidification of the mass sets in, is 
lowered into the box and left to cool. The block 
now furnishes a handle, and this should be wrapped 
round with paper, the sections cut with the keenest 



182 THE RAZOR 

possible razor, and as thin as possible, and placed 
in spirit as cut. Prom the spirit, which must be 
the strongest obtainable, they are placed in the 
clearing liquid, carbolic and turpentine, and then 
slid on to the slide, a drop of balsam placed on the 
section, and the cover over all. Of late years all 
sections of ordinary soft tissues, animal or vegetable, 
have been cut by one of the infiltration methods, 
in which the interstices of the tissue are filled up 
by some material which "prevents the relations of 
the cells from being altered during the process of 
cutting. To enter fully into this matter would 
occupy too much space, and would serve no useful 
purpose, for the worker who requires to make use 
of such means will find it indispensable to obtain 
Bolles Lee's Microtomist's Vade Mecum, in which 
the whole matter is exhaustively treated. 

The simple method above detailed will answer 
most ordinary purposes, provided that a few pre- 
cautions be attended to. The chief are as follows. 
The outside of the block of tissue must be suffi- 
ciently dry for the wax-and-oil to adhere to it. 
The razor must be extremely sharp, and must be 
kept so by application to a Turkey stone during the 
section-cutting. The blade must be drawn across 
the tissue from heel to point, and kept wetted with 
spirit the whole time, so as to prevent any dragging 
of the section. The transference of the section to 
the slide must be effected by means of a section- 
lifter, which may be made by beating out a piece 
of stout copper wire to a thin flat blade ; or a small 
palette-knife, or German-silver lifter, may be pur- 



DOUBLE STAINING 18.? 

chased for a few pence. The carbolic turpentine is 
best used by placing a little in a watch-glass, and 
floating the sections on to it by lifting them singly 
with the lifter, freeing them from superfluous spirit 
by draining on to blotting-paper, and allowing them 
to float on to the surface of the liquid in the watch- 
glass, so that the spirit may evaporate from above, 
and be replaced by the clearing agent from below 
The balsam solution should be thin, and the cover- 
glass must be allowed to settle down into place 
without pressure. 

The question of staining sections is a very large 
one, and is becoming of daily increasing com- 
plexity. 

We cannot go into it here, further than to say 
that most sections cut from unstained tissue will 
yield excellent results if stained first with Delafield's 
logwood solution (to be obtained at Baker's) to a very 
slight extent, and then with a solution of safranin. 
The sections should be washed with tap-water after 
the logwood stain, and should be of a pale violet 
colour. If over-stained, the colour may to a great 
extent be removed by washing with a very weak 
solution of hydrochloric acid, about two drops of 
acid to each ounce of water, and repeated washing 
in tap-water to remove the acid, and restore the 
violet. The safranin stain should be weak, and 
should be allowed to act for some time. From 
this last the sections are transferred to strong 
spirit, the latter being renewed until the sections 
cease to give up the red dye ; and they may then 
be mounted as described. The results with most 



1 84 CLEANLINESS ESSENTIAL 

tissues are superb, every detail of the structure 
being splendidly brought out. Safranin alone is 
also an admirable stain for many purposes. 

Further information must be sought in the book 
already mentioned. Let us, in closing, warn the 
beginner of two things which are of general appli- 
cation in practical microscopy. The first is, not to 
be discouraged by failures. The manipulations are 
in many cases very delicate, and premiums must be 
paid to experience for insurance against failure in 
every one of the processes. 

The second is, that the most scrupulous clean- 
liness will hardly suffice to prevent contamination 
of preparation by the all-pervasive dust which, 
invisible to the eye, assumes colossal proportions 
under the microscope, and the particles of which 
have an unpleasant habit of collecting on the most 
interesting or most beautiful portion of the pre- 
paration. This can only be guarded against by 
careful filtration of all fluids, and constant watch- 
fulness. 

A preparation properly made is a thing of beauty, 
and a joy for ever, — or if not for ever, at anyrate 
for many years ; and one such will repay an infini- 
tude of pains taken in its production. 



INDEX 





— — T 
PAOB 




PAGR 


AlR-PUMP . , 


. 174 


Convex lenses, virtua 


im- 


Algae 


. 78 


age 


. 11 


„ marine 


. 92 


Corallines . 


. 164 


Anemones, sea . 


. 159 


Corrosive sublimate . 


. 170 


Antennae . 


. 96 


Cover-glasses . . 


. 18 


Ants . 


. 97 










Desmids . 


. 81 


Bacillakia 


. 87 


Diatoms . 


. 85 


Balancers of Fly 


. 112 


,, preparation of . 175 


Bark 


. 61 


Dipping-tubes . 


. 22 


Blights . 


. 89 


Dissection 


. 20 


Blood, circulation of 


. 129 


,, instruments . 21 


„ corpuscles of 


. 128 


,, under microscope 24 


Bone 


. 123 


Drawing . 


. 25 


Breathing-tubes 


. 109 


,, squares . 


. 26 


Bull's-eye, use of 


. 32 










ECHINODERMS . 


. 162 


Camera lucida . 


. 25 


Entomostraca . 


. 152 


Canada Balsam . 


. 170 


Epidermis, animal . 


. 122 


Cartilage . 


. 124 


„ vegetable 


. 68 


Cells, animal . 


. 122 


Extemporised apparatus . 5 


,, circulation in 


. 40 






„ mounting dry i 


n . 173 


Feathers 


. 119 


„ pigment . 


121, 165 


Fish, scales of . 


' . 118 


,, spiral 


. 46 


,, parasites of 


. 153 


,, vegetable 


. 37 


Fixation of cell-forms 


. 171 


Ceramidia 


. 93 


Focus of mirror 


. 29 


Chlorophyll 


. 40 


Foraminifera 


. 156 


Compressorium, Bed 


.'s . 18 


Formalin . . . 


. 164 


Condenser, bull's-eye 


. 19 


Frog-plate . 


. 129 


,, substage 


. 19 






Confervas . 


. 84 


Gills of mussel . 


. 122 


Conjugation 


82, 84 


Gizzard of insects 


. 109 


Convex lenses . 


. 7 


Glycerine-gelatine . 


. 172 


,, foci of 


.7,8 


.. J el] y • 


. 171 


„ image f 


ormed 






by 


. 10 


Hairs, animal . • 


. 116 



13 



185 



1 86 



INDEX 



PAGB 

Hairs, vegetable . . 53 
Heads of Insects . . 104 

Illumination, correct 31, 32 
„ dark-field . 34 

,, for opaque 

objects . 33 
Imbedding . . .180 
„ by infiltration . 182 

Infusoria . . . .135 
Injection .... 164 
Insects . . . .97 
„ mounting of . . 177 

Jelly-fish . . .158 

Larva of Chironomus . 152 

Light, arrangement of .29 

Live-box . . . .17 

Logwood solution . . 183 

Magnification, to mea- 
sure . . . .27 
Mare's tail . . .91 

Marine life . . .155 
Microscope, Baker's . . 14 
,, „ "portable" 15 

,, primitive . 5 

,, simple . 12, 13 

Mildew .... 89 
Mirror, concave . . 29 
Mollusca . . . .161 
Mounting. . . . 168 
„ dry . . . 173 
,, foraminifera . 157 
Mosses . . . .96 
Muscle . . . .127 



Nails 
Needles 
Nerve 
Net . 
Nucleus 



124 

22 

127 

133 

40 



Objectives . .16 

Objects, drawing of . .24 

,, photography of . 36 

Oil-cells ... 58, 61 



FAGB 

Oscillatorise , , . 84 

Osmic acid , . .170 

Paeasites . . .153 

Petals . . . .69 

Picric acid . , .170 
Pigment .... 121 

Pocket magnifiers . .13 

Polariscope . . . 166 

Pollen . . . .71 

Polyzoa . . . .147 

Pond-hunting . . . 132 

Preservatives , , . 169 

Radiolabia . . . 157 

Rotifers . . . .147 

Safeanin stain . .183 

Sap . . . , 128 

Scent-glands . ', .57 

Sea- weeds . . , .92 

Section-cutting. . . 178 

Seeds . . . .75 

Skin 120 

Spiracles .... 102 

Sponge, fresh-water . .135 

,, spicules . .155 

Sporangia . . . .92 

Stage-forceps . . . 116 

Starch . . . .63 

,, mounting . . 172 

Stomata . . . .49 

Suckers . . , .108 

Teeth .... 125 

Troughs, glass . . .18 

Watee-beabs . . . 152 
Wings .... 110 

Wool . . . .116 

Worms, fresh-water . . 144 

,, marine . .160 

Yeast . . . .89 

Zocea . . . .161 

Zoophytes . . .157 

Zygnemaceae . . .85 



W. EEENDON AND SON, LIMITED, PLYMOUTH 




BY THE BAIRNIES